Two-dimensional addessable array of piezoelectric MEMS-based active cooling devices

ABSTRACT

A cooling system and method for using the cooling system are described. The cooling system includes a plurality of individual piezoelectric cooling elements spatially arranged in an array extending in at least two dimensions, a communications interface and driving circuitry. The communications interface is associated with the individual piezoelectric cooling elements such that selected individual piezoelectric cooling elements within the array can be activated based at least in part on heat energy generated in the vicinity of the selected individual piezoelectric cooling elements. The driving circuitry is associated with the individual piezoelectric cooling elements and is configured to drive the selected individual piezoelectric cooling elements.

CROSS REFERENCE TO OTHER APPLICATIONS

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/717,474 entitled PIEZO ELECTRIC MEMS-BASED ACTIVE COOLING FORHEAT DISSIPATION IN COMPUTE DEVICES filed Aug. 10, 2018 which isincorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

As semiconductor devices become increasingly powerful, the heatgenerated during operations also grows. For example, processors formobile devices such as smartphones, tablets and notebooks can operate athigh clock speeds, but produce a significant amount of heat. Because ofthe quantity of heat produced, processors may run at full speed only fora relatively short period of time. After this time expires, throttling(e.g. slowing of the processor's clock speed) occurs. Althoughthrottling can reduce heat generation, it also adversely affectsprocessor speed. As a result, performance of devices using theprocessors suffers. As technology moves to 5G and beyond, this issue isexpected to be exacerbated.

Various mechanisms to address the generation of heat are known. Largerdevices, such as laptop or desktop computers include an electric fanthat can be energized in response to an increase in temperature ofinternal components. However, such fans are typically too large formobile devices such as smartphones, may have limited efficacy because ofthe boundary layer of air existing at the surface of the components,provide a limited airspeed for air flow across the surface of thedevices and may generate an excessive amount of noise. Passive coolingsolutions may include a heat spreader and a heat pipe or vapor chamberto transfer heat to a heat exchanger. Although a heat spreader somewhatmitigates the temperature increase at hot spots, the amount of heatproduced in current and future devices may not be adequately addressed.Similarly, a heat pipe or vapor chamber may provide an insufficientamount of heat transfer to address excessive heat generated.Accordingly, additional cooling solutions are desired.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIGS. 1A-1D are diagrams depicting exemplary embodiments of a coolingsystem usable with a structure.

FIGS. 2A-2B are diagrams depicting an exemplary embodiment of apiezoelectric cooling system usable with a structure.

FIG. 3 is a diagram depicting an exemplary embodiment of a piezoelectriccooling system usable with a structure.

FIGS. 4A-4D are diagrams depicting exemplary embodiments of apertures,orifices and piezoelectric/chamber shapes in a piezoelectric coolingsystem usable with a structure.

FIGS. 5A-5C is a diagram depicting an exemplary embodiment of apiezoelectric cooling system and diagrams depicting an exemplaryembodiment of the movement of the actuator and orifice plate valve.

FIG. 6 is a diagram depicting an exemplary embodiment of a piezoelectriccooling system.

FIG. 7 is a diagram depicting an exemplary embodiment of a piezoelectriccooling system.

FIGS. 8A-8E are diagrams depicting exemplary embodiments of apiezoelectric cooling system usable with a structure.

FIGS. 9A-9C are diagrams depicting an exemplary embodiment of apiezoelectric cooling system usable with a structure.

FIGS. 10A-10C are diagrams depicting an exemplary embodiment of apiezoelectric cooling system usable with a structure.

FIG. 11 is a diagram depicting an exemplary embodiment of apiezoelectric cooling system.

FIGS. 12A-12D are diagrams depicting exemplary embodiments ofpiezoelectric cooling systems.

FIGS. 13A-13E are diagrams depicting exemplary embodiments of orificeplates for a piezoelectric cooling system.

FIGS. 14A-14D are diagrams depicting exemplary embodiments of coolingsystems usable with structures.

FIGS. 15A-15K are diagrams depicting exemplary embodiments of coolingsystems usable with structures.

FIG. 16 is a diagram depicting an exemplary embodiment of a coolingsystem.

FIGS. 17A-17B are diagrams depicting exemplary embodiments of coolingsystems usable with a structure.

FIG. 18 is a diagram depicting an exemplary embodiment of a coolingsystem usable with a semiconductor structure.

FIG. 19 is a diagram depicting an exemplary embodiment of a mobiledevice incorporating a piezoelectric cooling system.

FIGS. 20A-20B are diagrams depicting exemplary embodiments of coolingsystems and associated electronics.

FIG. 21 is a flow chart depicting an exemplary embodiment of a methodfor operating a cooling system usable with a structure.

FIG. 22 is a flow chart depicting an exemplary embodiment of a methodfor operating a cooling system.

FIG. 23 is a flow chart depicting an exemplary embodiment of a methodfor operating a cooling system.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

A cooling system and method for using the cooling system are described.The cooling system includes a plurality of individual piezoelectriccooling elements spatially arranged in an array extending in at leasttwo dimensions, a communications interface and driving circuitry. Thecommunications interface is associated with the individual piezoelectriccooling elements such that selected individual piezoelectric coolingelements within the array can be activated based at least in part onheat energy generated in the vicinity of the selected individualpiezoelectric cooling elements. The driving circuitry is associated withthe individual piezoelectric cooling elements and is configured to drivethe selected individual piezoelectric cooling elements.

FIGS. 1A-1D are diagrams depicting exemplary embodiments of coolingsystems 100 and 100A usable with a structure. For clarity, only certaincomponents are shown and FIGS. 1A-1D are not to scale. FIGS. 1A-1Cdepict operation of cooling system 100, while FIG. 1D depicts coolingsystem 100A. Referring to FIGS. 1A-1C, the cooling system 100 is used inconnection with a structure 130. Structure 130 generates or conductsheat from a nearby heat-generating object during operation and isdesired to be cooled. Structure 130 may include semiconductorcomponents(s) including individual integrated circuit components such asprocessors, other integrated circuit(s) and/or chip package(s);sensor(s); optical device(s); one or more batteries; or othercomponent(s) of an electronic device such as a computing device; otherelectronic component(s) and/or other device(s) desired to be cooled andwhich may have limited space in which to place a cooling system. Suchcomputing devices may include but are not limited to smartphones, tabletcomputers, laptop computers, hand held gaming systems, digital cameras,virtual reality headsets, augmented reality headsets, mixed realityheadsets and other devices. Thus, cooling system 100 may be amicro-electro-mechanical system (MEMS) cooling system capable ofresiding within mobile computing devices. For example, the total height,d, of cooling system 100 may be less than one millimeter and in someembodiments does not exceed two hundred and fifty microns.

Cooling system 100 includes three cooling cells 101 in the embodimentshown. In other embodiments, another number of cooling cells 101 may beincluded and/or the cooling cells 101 may be arranged in another manner.For example, cooling cells 101 may be arranged in groups in order tocool selected portions of the structure 130. In some embodiments,cooling cells 101 may be included in one or more two-dimensional coolingarrays for a computing device. Cooling system 100 is also incommunication with a fluid used to cool structure 130. In someembodiments, the fluid substantially surrounds cooling cells 101. Thefluid may be a gas or a liquid. For example, in some embodiments, thefluid is air.

Each cooling cell 101 includes cooling element 110 that is in contactwith a fluid. For clarity, only one cooling element 110 is labeled.Cooling element 110 has a first side distal from the structure 130 and asecond side proximate to the structure 130. In some embodiments, coolingelement 110 is substantially solid and flat. In the embodiment shown inFIGS. 1A-1C, the first side of cooling element 110 is the top of coolingelement 110 and the second side is the bottom of cooling element 110.Cooling element 110 is actuated to vibrate as shown in FIGS. 1A-1C. Forexample, cooling element 110 may include a piezoelectric structure (notseparately shown in FIGS. 1A-1D) residing on a substrate (not separatelyshown in FIGS. 1A-1D). Cooling element 110 may thus be a piezoelectriccooling element. Consequently, cooling element 110 and analogous coolingelements are referred to hereinafter as piezoelectric cooling elementthough it is possible that a mechanism other than a piezoelectric mightbe used to drive the cooling element in some embodiments. In someembodiments, piezoelectric cooling element 110 includes a piezoelectriclayer on a stainless steel and/or Hastelloy substrate. In addition tothe piezoelectric structure, piezoelectric cooling element 110 may alsoinclude one or more electrodes (not shown in FIGS. 1A-1D) used to drivethe piezoelectric structure. Other layers (not shown) including but notlimited to seed, capping, passivation or other layers might be includedin piezoelectric cooling element 110 in some embodiments. Further, insome embodiments, cooling element 110 is “breathable”, or capable ofdriving fluid from one side of the cooling element to the other using avibrational motion (in contrast to a rotating motion of a fan blade).For example, cooling element 110 may vibrate closer to and further fromstructure 130 to drive fluid from the first (distal) side to the second(proximal) side. Such a capability is generally desired when coolingelement 110 is used to cool structure 130. In such embodiments, coolingelement 110 may have valve(s) and/or aperture(s) therein. In otherembodiments, cooling element 110 may be used to macroscopically drivethe fluid. In such embodiments, cooling element 110 may be further fromsurrounding structures and may not include a valve and/or aperturetherein. However, for clarity, such structures are not shown in FIGS.1A-1D.

Also shown in cooling cell 101 is orifice plate 120 having orifices 122therein. Although one orifice 122 is shown for each cooling cell, inother embodiments, multiple orifices may be provided for each coolingcell 101. Further, the orifice 122 is shown as being centrally locatedin cooling cell 101. In other embodiments, orifice(s) 122 may be locatedelsewhere. Although symmetry may be desired, cooling cells 101 are notrequired to be symmetric. A single orifice plate 120 for multiplecooling cells 101 is shown in FIGS. 1A-1D. In other embodiments,multiple orifice plates may be used. For example, in some embodiments,each cooling cell 101 may have a separate orifice plate 120. In anotherembodiment, orifice plate 120 may be removed or orifices 122 may beconsidered to occupy substantially all of the region betweenpiezoelectric cooling element 110 and structure 130.

As discussed above, cooling system 100 may be a MEMS device. Thus, thedimensions of cooling system 100 may be small. For example, coolingcells 101 may have a rectangular footprint with sides having a length,S, of not more than seven millimeters. In some such embodiments, S maybe at least three millimeters. In some embodiments, cooling cells 101are square. Orifice plate 120 may be located a distance, h, from theclosest surface of structure 130 that is generating heat. In someembodiments, h is at least fifty microns and not more than five hundredmicrons. In some embodiments, h is not more than two hundred microns. Insome embodiments, h is at least one hundred microns. Orifice plate 120may have a thickness of at least ten and not more than twenty-fivemicrons in some embodiments. The depth, d, of cooling cells 101 may beat least forty microns and not more than five hundred microns. In someembodiments, d is at least fifty microns and not more than three hundredmicrons. Thus, piezoelectric cooling elements 110 may be at least fortyand not more than five hundred microns from orifice plate 120.Piezoelectric cooling elements 110 may be at least fifty and not morethan five hundred microns from structure 130. In some embodiments,orifice plate 120 is at least fifty and not more than one hundred fiftymicrons thick. For example, orifice plate 120 may be nominally onehundred microns thick. In some embodiments, the entire thickness ofcooling system 100 (e.g. h added to d) is not more than five hundredmicrons. In some embodiments, the entire thickness of cooling system 100is at least two hundred fifty microns. In some embodiments, thediameters, δ, of orifices 122 are at least fifty microns and not morethan two hundred microns. In some embodiments, orifices 122 occupy atleast two percent and not more than five percent of the portion of theorifice plate 120 below cooling element 110. Thus, cooling element 110and orifice plate 120 may be viewed as forming a chamber for eachcooling cell 101. Such a chamber has an orifice 122 proximate tostructure 130 that is generating heat. Although each cooling cell 101 isshown as identical (e.g. to within manufacturing tolerances), in otherembodiments, different cooling cells 101 in a single array may beconfigured differently. For example, the diameter of the orifices, δ,the size S of the cell, and the depth, d, might differ. Further, asdescribed below, cells 101 need not be driven in the same manner. Forexample, the amplitude of deflection and/or phase of cooling elements110 may differ. In some embodiments, some cooling cells 101 are driven,while others are dormant.

FIG. 1A depicts piezoelectric cooling element 110 in a neutral position.Thus, cooling elements 110 are shown as substantially solid and flat. Inoperation, piezoelectric cooling elements 110 are actuated to vibratebetween positions shown in FIGS. 1B and 1C. Referring to FIG. 1B,piezoelectric cooling element 110 in each cell 101 has been actuated tomove away from (deform to be convex) structure 130. The neutral positionof piezoelectric cooling elements 110 are shown by dotted lines. In someembodiments, cooling elements 110 include a fluid entry path (not shownin FIGS. 1A-1D) that allows the fluid to move from the distal side tothe proximal side of cooling element 110, increasing the volume of fluidin the chambers formed by orifice plate 120 and piezoelectric coolingelements 110. For example, cooling elements 110 may include one or moreapertures that are opened when actuated in a manner analogous to thatshown in FIG. 1B. Such a fluid entry path would be substantially orcompletely closed in the situation shown in FIG. 1C. For example,cooling elements 110 may include active or passive valve(s) or analogousstructure(s). In other embodiments, the fluid entry path may be formedin another region. For example, a valve may be included in the sides ofcooling cells 101 or at the edges of piezoelectric cooling elements 110in location(s) that allow fluid to be drawn from the distal to theproximal side of piezoelectric cooling elements 110. In someembodiments, aperture(s) may be located near the edges of coolingelements 110. In some embodiments, each cell 101 also includes one ormore valves (not shown in FIGS. 1A-1D) for orifice plate 120. Such avalve substantially or completely closes orifices 122 when coolingelement 110 draws fluid from the distal to the proximal side as shown inFIG. 1B. Such a valve improves the efficiency of the movement of fluidfrom the distal to the proximal side of cooling element 110. However, inalternate embodiments, such a valve might be omitted.

In the situation shown in FIG. 1C, piezoelectric cooling element 110 ineach cell 101 has been actuated to move toward (deform to be concave)structure 130. The neutral position of piezoelectric cooling elements110 are shown by dotted lines. Thus, the volume of fluid in the chambersformed by orifice plate 120 and piezoelectric cooling elements 110 hasdecreased. The volume of the chamber for each cooling cell 101 formed byorifice plate 120 and cooling element 110 may vary between one hundredtwenty-five percent (FIG. 1B) and seventy-five percent (FIG. 1C) of theneutral volume (FIG. 1A). For example, in some embodiments, cells 101having a depth, d, of at least one hundred microns, the peak-to-peakdeflection (distance between the top of cooling element 110 in FIG. 1Band the top cooling element 110 in FIG. 1C) may be up to fifty microns.In some embodiments, the deflection of cooling element 110 is desired tobe large in order to increase the volume of flow and/or speed of fluidthrough orifices 122. In such embodiments, the peak-to-peak deflectionmay be at least one hundred microns for a cell having a longest side(e.g. length S) of three through five millimeters. Other deflections arepossible for other cell sizes. However, in some embodiments, thepercentage change in volume is less than ten percent and greater than0.1 percent. In some such embodiments, the percentage change in volumeis less than five percent and greater than 0.1 percent. For example, thedeflection of piezoelectric cooling element 110 may be ten microns orless for a height d of three hundred microns. In the embodiments above,cooling elements 110 may also be driven at resonance for reduced poweroperation, as described below. Cooling cells 101 are capable of movingfluid through orifices 122 to cool structure 130 in both cases.

Due to the vibrational motion of cooling elements 110 (and the attendantdecrease in volume of the chamber from FIG. 1B to FIG. 1C), the fluid ispushed by cooling elements 110 through orifices 122 (not labeled in FIG.1C for clarity). The motion of the fluid is shown by arrows throughorifices 122. The fluid may spread as it travels away from orifice plate120, as shown by dashed arrows in FIG. 1C. The fluid deflects off of thesurface of structure 130 and travels along the channel betweensemiconductor structure 130 and orifice plate 120. Although all coolingcells 101 are shown in FIGS. 1A-1C as operating in phase, in otherembodiments, cooling elements 110 may be out of phase or some coolingelements 110 are selectively actuated while other cooling elements 110remain in the neutral position.

The motion between the positions shown in FIGS. 1B and 1C may berepeated. Thus, piezoelectric cooling elements 110 vibrate, drawingfluid from the distal to the proximal side of cooling elements 110 andpushing the fluid through orifices 122 and toward semiconductorstructure 120. In some embodiments the frequency of vibration ofpiezoelectric cooling element(s) 110 during operation is at least 15kHz. In some embodiments, the frequency is at least 20 kHz. Thus,piezoelectric cooling elements 110 may operate in the ultrasonic range.In some embodiments, the speed at which the fluid impinges on thesurface of structure 130 is at least thirty meters per second. In someembodiments, the fluid is driven by piezoelectric cooling elements 110at a speed of at least forty meters per second. In some suchembodiments, the fluid has a speed of at least forty-five meters persecond. In some embodiments, the fluid has a speed of at leastfifty-five meters per second. Further, in some embodiments, fluid speedsof at least sixty meters per section and/or seventy-five meters persecond may be achieved. However, higher speeds may be possible in someembodiments. Fluid speeds in the range of thirty meters per second ormore may be achievable in part due to judicious selection of thediameters, δ, of orifices 122.

As indicated in FIG. 1C, the fluid driven toward structure 130 may movesubstantially normal (perpendicular) to the surface of structure 130. Inother embodiments, the fluid motion may have a nonzero acute angle withrespect to the normal to the surface of structure 130. In either case,the fluid may thin and/or form apertures in the boundary layer of fluidat the surface of structure 130. The boundary layer in one case isindicated by the curved dotted lines at the surface of structure 130 inFIG. 1C. As a result, transfer of heat from structure 130 may beimproved. The fluid deflects off of the surface of structure 130,traveling along the surface of semiconductor structure 130. In someembodiments, the fluid moves in a direction substantially parallel tothe surface of structure 130. Thus, heat from structure 130 may beextracted by the fluid. The fluid may exit the region between orificeplate 120 and semiconductor structure 130 at the edges of cooling cells101. In other embodiments, chimneys (not shown in FIGS. 1A-1D) betweencooling cells 101 allow fluid to be carried away from semiconductorstructure 130 between cooling cells 101. In either case, the fluid mayreturn to the distal side of cooling elements 110 where the fluid mayexchange the heat transferred from structure 130 to another structure orto the ambient environment. The fluid may then be circulated throughcooling cells 101 to extract additional heat. As a result, structure 130may be cooled.

FIG. 1D depicts cooling system 100A analogous to cooling system 100.Cooling system 100A may be MEMS systems having dimensions in the rangesdescribed above. Piezoelectric cooling system 100A operates in a manneranalogous to piezoelectric cooling system 100. In the embodiment shown,an additional fluid flow substantially parallel to the surface ofstructure 130 is provided. This is depicted by arrows substantiallyparallel to the surface of structure 130. Although shown in oppositedirection, in other embodiments, the fluid flow may be in the samedirection. Consequently, motion of fluid along the surface of structure130 may be increased, allowing for improved heat transfer.

Cooling systems 100 and 100A may more efficiently dissipate heat fromstructure 130. Because fluid impinges upon structure 130 with sufficientspeed and in some embodiments substantially normal to the surface ofstructure 130, the boundary layer of fluid at the surface of structure130 may be thinned and/or partially removed. Consequently, heat transferbetween structure 130 and the moving fluid is improved. In someembodiments, the heat transfer may be at least three through six timesthe heat transfer if an electric fan were to blow air of equivalent massflow parallel or orthogonal to the surface of structure 130. Becausestructure 130 is more efficiently cooled, structure 130 may be run athigher speed and/or power for longer times. For example, if structure130 includes a high-speed processor, such a processor may be run forlonger times before throttling. Thus, performance of a device utilizingstructure 130 may be improved. Further, cooling systems 100 and 100A areMEMS devices. Thus, cooling systems 100 and 100A are small-having atotal height not exceeding five hundred microns in some embodiments.Consequently, cooling systems 100 and 100A are suitable for use inmobile devices, such as smart phones, other mobile phones, virtualreality headsets, wearables and handheld games, in which limited spaceis available. Performance of mobile devices may thus be improved.Cooling systems 100 and 100A may also be used in other computedevices-both mobile (such as those discussed above and laptop computers)and non-mobile (such as desktop computers or smart televisions). Becausepiezoelectric cooling elements 110 may be vibrated at frequencies of 15kHz or more, users may not hear any noise associated with actuation ofcooling elements 110. If driven at or near resonance frequency for thepiezoelectric cooling elements 110, the power used in operating coolingsystems 100 and 100A may be significantly reduced. Thus, the benefits ofimproved, quiet cooling may be achieved with limited additional power.The cooling power of system 100 and/or 100A may be further tuned byengineering the number of cells 101 used and/or the voltage at whicheach cell is driven. Consequently, performance of devices incorporatingcooling systems 100 and/or 100A may be improved.

FIGS. 2A-2B are diagrams depicting an exemplary embodiment of apiezoelectric cooling system 200 usable with a semiconductor structure.FIGS. 2A and 2B are cross-sectional views taken at an angle from eachother. For clarity, only certain components are shown and FIGS. 2A-2Bare not to scale. Piezoelectric cooling system 200 is used in connectionwith a structure 230. Structure 230 generates heat during operation andis desired to be cooled. Structure 230 is analogous to structure 130.Piezoelectric cooling system 200 may fit within mobile computing devicesand is a MEMS cooling device. Piezoelectric cooling system 200 may alsobe viewed as a single cell in a larger cooling system that may includemultiple cells/piezoelectric cooling systems 200. Also shown in FIGS.2A-2B is back plate 250 which may be part of the device, such as a smartphone or other mobile phone, in which piezoelectric cooling system 200resides.

Piezoelectric cooling system 200 includes piezoelectric cooling element210 that is analogous to piezoelectric cooling elements 110 and orificeplate 220 that is analogous to orifice plate 120. Orifice plate 220 thusincludes multiple apertures 222 (of which only two are labeled)analogous to apertures 122. Also shown are valve 215, chimneys 240,spacers 241, 242 and 243 and leads 270, 272, 274 and 276. Spacers 241separate orifice plate 220 from structure 230.

Piezoelectric cooling system 200 may be a MEMS device and thus may havedimensions analogous to those described above. Piezoelectric coolingsystem/cell 200 may have a rectangular footprint with sides having alength, S, of at least three millimeters and not more than sevenmillimeters. In the embodiment shown, piezoelectric cooling system 200is square. Other footprints are, however, possible. Spacer 241 has aheight, h, of at least than fifty microns and not more than two hundredmicrons. In some embodiments, h is at least one hundred microns. Spacers242 have a depth, d, of at least fifty microns and not more than threehundred microns. In some embodiments, spacers 242 are at leastseventy-five microns and not more than two hundred microns in height.Cooling element 210 may be at least thirty microns thick and not morethan fifty microns thick. In some embodiments, orifice plate 220 is atleast fifty and not more than one hundred fifty microns thick. In someembodiments, the entire thickness of piezoelectric cooling system 200 isat least two hundred and fifty microns and not more than five hundredmicrons. In some embodiments, the diameter, δ, of orifices 222 are atleast fifty microns and not more than two hundred microns. In someembodiments, orifices 222 are at least one hundred microns and not morethan two hundred microns wide. In other embodiments, other widths arepossible. In some embodiments, orifices 222 occupy at least two percentand not more than five percent of the portion of the orifice plate 220below cooling element 210. Spacers 243 are standoffs to the back plate250. Spacers 243 protect piezoelectric cooling element 210 and valve 215from physically contacting back plate 250 (or other structure) duringoperation.

Also shown are chimneys 240. As indicated more clearly in FIG. 2B,chimneys 240 provide a return path for fluid from near structure 230 (onthe proximal side of piezoelectric cooling element 210) to the distalside of piezoelectric cooling element 210. In the embodiment shown,chimneys 240 have a width, w, of at least 0.75 mm to not more than 1.5mm. The pressure differential between the center of piezoelectriccooling system 200 and edges/chimneys 240 is desired to be small topromote the free flow of the fluid through the system. In someembodiments the area of each chimney 240 exceeds the total area of allof the orifices 222. In the embodiment shown, there are four chimneysfor each piezoelectric cooling system/cell 200. Consequently, chimneys240 have greater than four times the total area of orifices 222. Inanother embodiment, a different number of chimneys may be used.

Piezoelectric cooling element 210 is a multilayer structure. Threelayers 211, 212 and 213 are shown. In some embodiments, piezoelectriccooling element 210 may include additional layers such as seed andpassivation layers (not shown). In some embodiments, piezoelectriccooling element 210 is at least ten microns thick and not more thantwenty-five microns thick. Piezoelectric cooling element 210 includes asubstrate 211, piezoelectric layer 212 and actuator electrode 213. Insome embodiments, substrate 211 is stainless steel and/or Hastelloy.Stainless steel and/or Hastelloy may be selected because of itsrelatively low coefficient of thermal expansion, stiffnesscharacteristics, high fatigue life and ability to undergo hightemperature processing in formation of piezoelectric cooling element210. As can be seen in FIG. 2A, substrate 211 and actuator electrode 213are connected to leads 270 and 272, respectively. By driving a voltagedifference between leads 270 and 272, and thus between actuatorelectrode 213 and substrate 211, piezoelectric layer 212 can be inducedto move. Consequently, piezoelectric cooling element 210 vibrates, asdescribed above. In the embodiment shown, piezoelectric cooling element210 also includes an aperture 214. In the embodiment shown,piezoelectric cooling element 210 includes a single aperture 214 that iscentrally located. In other embodiments, piezoelectric cooling element210 may include another number of apertures and/or include aperture(s)that are not centrally located.

Valve 215 includes a substrate 216, piezoelectric layer 217 andelectrode 218. In some embodiments, valve 215 is at least ten micronsthick and not more than twenty-five microns thick. Thus, valve 215 maybe analogous to piezoelectric cooling element 210 and can be consideredto be a piezoelectric valve element. In the embodiment shown, substrate216 and electrode 217 are coupled with leads 274 and 276, respectively.Although four leads are shown for valve 215 and piezoelectric coolingelement 210, in another embodiment, fewer leads may be used. Forexample, a three lead configuration including a ground lead and leads toelectrodes 213 and 218 may be present. Valve 215 also includes apertures219. In the embodiment shown, valve 215 includes four apertures 219. Inother embodiments, another number of apertures orifices may be present.For example, two apertures might be used instead of four. Apertures 219are, however, offset from aperture 214 in piezoelectric cooling element210. Thus, when valve 215 and piezoelectric cooling element 210 are incontact, as shown in FIGS. 2A-2B, fluid is prevented from moving throughpiezoelectric cooling element 210, from the distal to proximal side orvice versa. If valve 215 and piezoelectric cooling element 210 are notin physical contact, cooling fluid may move through apertures 219 and214.

In operation, piezoelectric cooling system 200 functions in a manneranalogous to cooling system 100. Valve 215 and piezoelectric coolingelement 210 are actuated to move away from structure 230. Further, valve215 may be driven to move faster and/or further than piezoelectriccooling element 210. Thus, fluid is drawn from the distal side ofpiezoelectric cooling element 210 to the proximal side. Valve 215 andpiezoelectric cooling element 210 are actuated to move toward fromstructure 230. Further, valve 215 is driven to move faster and/orfurther than piezoelectric cooling element 210. Consequently, valve 215contacts piezoelectric cooling element 210, preventing the flow of fluidthrough piezoelectric cooling element 210. Piezoelectric cooling element210 also pushes fluid in the chamber between element 210 and orificeplate 220 toward structure 230. The fluid moves through orifices 220 andtoward structure 230, in a manner analogous to that described above. Asdiscussed above, piezoelectric cooling element may be driven at or nearresonance and at frequencies of 15 kHz or more.

Piezoelectric cooling system 200 may more efficiently dissipate heatfrom structure 230. Because fluid impinges upon structure 230 withsufficient speed and in some embodiments substantially normal to thesurface of structure 230, the boundary layer of fluid at the surface ofstructure 230 may be thinned and/or partially removed. Consequently,heat transfer between structure 230 and the moving fluid is improved.Because structure 230 is more efficiently cooled, structure 230 may berun at higher speed and/or power for longer times. Thus, performance ofa device utilizing structure 230 may be improved. Further, coolingsystem 200 is a MEMS device having the dimensions described above. Thus,piezoelectric cooling system 200 is suitable for use in mobile devices,such as smart phones, in which limited space is available. Piezoelectriccooling system 200 may also be used in other compute devices-both mobileand non-mobile. Performance of such devices may thus be improved.Because piezoelectric cooling elements 210 may be vibrated at ultrasonicfrequencies and/or at or near resonance, piezoelectric cooling system200 may be quieter and consume less power. Thus, the benefits ofimproved, quiet cooling may be achieved with limited additional power.Consequently, performance of devices incorporating cooling system 200may be improved.

FIG. 3 is a diagram depicting an exemplary embodiment of piezoelectriccooling system 300. For clarity, only certain components are shown andFIG. 3 is not to scale. Piezoelectric cooling system 300 is used inconnection with a structure 330 and includes a cell 301. Structure 330generates heat during operation and is desired to be cooled. Structure330 is analogous to structure 130. Piezoelectric cooling system 300 mayfit within mobile computing devices and is a MEMS cooling device.Piezoelectric cooling system 300 may also be viewed as a single cell ina larger cooling system that may include multiple cells/piezoelectriccooling systems 300. Also shown in FIG. 3 is plate 350 which may be partof the device, such as a smart phone, in which piezoelectric coolingsystem 300 resides. However, plate 350 might be replaced with anothercomponent.

Piezoelectric cooling system 300 includes piezoelectric cooling element310 that is analogous to piezoelectric cooling elements 110 and 210 andorifice plate 320 that is analogous to orifice plate(s) 120 and 220.Orifice plate 320 thus includes multiple apertures 322 (of which onlytwo are labeled) analogous to apertures 122 and 222. Also shown arevalve 315, chimneys 340, spacers 341, 342 and 343 and leads 370, 372,374 and 376. Spacers 341 separate orifice plate 320 from structure 330.Leads 370, 372, 374 and 376 are used to drive cooling element 310 andvalve 315.

Piezoelectric cooling system 300 may be a MEMS device and thus may havedimensions analogous to those described above. Piezoelectric coolingsystem 300 is similar to piezoelectric cooling system 200. However, theapertures in cooling element 310 and valve 315 have been changed. Inparticular, valve 315 having substrate 316, piezoelectric 316 andelectrode 318 has a central aperture 319. Cooling element 310 havingsubstrate 311, piezoelectric 312 and electrode 313 has apertures 314that are offset from the center. Active valve 315 still functions in ananalogous manner to valve 215.

In operation, piezoelectric cooling system 300 functions in a manneranalogous to cooling systems 100 and 200. Valve 315 and piezoelectriccooling element 310 are actuated to move away from structure 330. Valve315 may be driven to move faster and/or further than piezoelectriccooling element 310. Thus, fluid is drawn from the distal side ofpiezoelectric cooling element 310 to the proximal side. Piezoelectriccooling element 310 also pushes fluid in the chamber between element 310and orifice plate 320 toward structure 330. The fluid moves throughorifices 320 and toward structure 330, in a manner analogous to thatdescribed above.

Piezoelectric cooling system 300 may more efficiently dissipate heatfrom structure 330. Because structure 330 is more efficiently cooled,structure 330 may be run at higher speed and/or power for longer times.Thus, performance of a device utilizing structure 330 may be improved.Further, cooling system 300 is a MEMS device having the dimensionsdescribed above. Thus, piezoelectric cooling system 300 is suitable foruse in mobile devices, such as smart phones, in which limited space isavailable. Piezoelectric cooling system 300 may also be used in othercompute devices-both mobile and non-mobile. Performance of such devicesmay thus be improved. Because piezoelectric cooling elements 310 may bevibrated at ultrasonic frequencies and/or at or near resonance,piezoelectric cooling system 300 may be quieter and consume less power.Thus, the benefits of improved, quiet cooling may be achieved withlimited additional power. Consequently, performance of devicesincorporating cooling system 300 may be improved.

FIGS. 4A-4D are diagrams depicting exemplary embodiments of apertures,orifices and piezoelectric/chamber shapes in piezoelectric coolingsystems 400A, 400B, 400C and 400D, respectively. For clarity, onlycertain components are shown and FIGS. 4A-4D are not to scale. Otherconfigurations of apertures are possible. FIG. 4A depicts piezoelectriccooling system 400A including aperture 414A for a corresponding coolingelement 410A and apertures 419A for a corresponding valve. Thus, theconfiguration shown in FIG. 4A may be used in a cooling cell such as thecooling cell 200. In an alternate embodiment, apertures 419A might beused for a cooling element and aperture 414A for a valve. Because oftheir alignment, apertures 414A and 419A may allow fluid to flow freelyfrom the distal to the proximal side of the cooling element when thevalve and cooling element are not in contact. When the valve and coolingelement are in contact, apertures 414A and 419A are closed, preventingsuch a movement of fluid. Thus, the cooling element can push fluidthrough the orifices such that the fluid reaches higher speeds asdescribed above. Also shown are the locations of portions of chimneys440 corresponding to chimneys 240. In the embodiments, only a singlecell that may be present in a multiple-cell system is shown.Consequently, the portion of chimneys 440 may be one-fourth of thechimneys used.

FIG. 4B depicts piezoelectric cooling system 400B including apertures414B for a corresponding cooling element 410B and aperture 419B for acorresponding valve. Thus, the configuration shown in FIG. 4B may beused in a cooling cell such as the cooling cell 300. In an alternateembodiment, aperture 419B might be used for a cooling element andaperture 414B for a valve. Because of their alignment, apertures 414Band 419B may allow fluid to flow freely from the distal to the proximalside of the cooling element when the valve and cooling element are notin contact. Apertures 414B and 419B preventing such a movement of fluid.When the valve and cooling element are in contact. Thus, the coolingelement can push fluid through the orifices such that the fluid reacheshigher speeds as described above. Also shown are the locations ofportions of chimneys 440 corresponding to chimneys 340.

Using the configurations of apertures in cooling systems 400A and 400B,the apertures can function as a valve. Thus, movement of fluid from thedistal to proximal side of the cooling element when desired may beimproved. When fluid is desired to be prevented from moving from oneside to the other of the cooling element when such a flow isundesirable. Thus, performance of a cooling element and valveincorporating an analogous configuration of apertures may be enhanced.

FIGS. 4C and 4D depict piezoelectric cooling systems 400C and 400Dhaving piezoelectric cooling elements 410C and 410D, respectively. Forsimplicity, the configuration of apertures 414C/414D for piezoelectriccooling elements 410C/410D and apertures 419C/419D for the correspondingvalve remains unchanged from that shown in FIG. 4A. For simplicity, thechimneys are not shown in FIG. 4C. Piezoelectric cooling elements 410A,410C and 410D corresponding chamber shapes differ. Chamber andpiezoelectric cooling element 410A are square. Chamber and piezoelectriccooling element 410C are octagonal. Chamber and piezoelectric coolingelement 410D are rectangular. As discussed above, a piezoelectriccooling element may be driven at resonance and this resonance may be ata frequency of 15 kHz or higher. Chambers and/or piezoelectric coolingelements 410A, 410C and/or 410D have different shapes and, therefore,may have different resonance frequencies. This and other mechanisms maybe used to modify the resonant frequency of the chamber andpiezoelectric cooling elements 410A, 410C and 410D. Thus, the resonantfrequencies of piezoelectric cooling system 400A, 400B, 400C and 400Dmay be engineered to be in the desired, target range.

FIGS. 5A-5C is a diagram depicting an exemplary embodiment of apiezoelectric cooling system 500 and diagrams depicting an exemplaryembodiment of the movement of the actuator and orifice plate valve. Forclarity, only certain components are shown and FIG. 5A is not to scale.Piezoelectric cooling system 500 is used in connection with a structure530 and includes a cell 501. Structure 530 generates heat duringoperation and is desired to be cooled. Structure 530 is analogous tostructure 130. Piezoelectric cooling system 500 may fit within mobilecomputing devices and is a MEMS cooling device. Piezoelectric coolingsystem 500 may also be viewed as a single cell in a larger coolingsystem that may include multiple cells 501/piezoelectric cooling systems500. Also shown in FIG. 5 is plate 550 which may be part of the device,such as a smart phone, in which piezoelectric cooling system 500resides. However, plate 550 might be replaced with another component.

Piezoelectric cooling system 500 includes piezoelectric cooling element510 that is analogous to previously discussed piezoelectric coolingelements and orifice plate 520 that is analogous to previously describedorifice plate(s). Piezoelectric cooling element 510 includes substrate511, piezoelectric layer 512 and electrode 513 having apertures 514 thatare offset from the center. Orifice plate 520 thus includes multipleapertures 522 (of which only one is labeled). Also shown are passivevalve 515, chimneys 540, spacers 541, 542 and 543 and leads 570 and 572.Spacers 541 separate orifice plate 520 from structure 530. Leads 570 and572 are used to energize cooling element 510 to vibrate.

Piezoelectric cooling system 500 may be a MEMS device and thus may havedimensions analogous to those described above. Piezoelectric coolingsystem 500 is similar to piezoelectric cooling systems 200 and 300.However, valve 515 is a passive valve. Thus, when cooling element 510 isactuated to move away from structure 530, cooling element 510 move awayfrom valve 515. Apertures 514 open and fluid flows from the distal tothe proximal side of cooling element 510. In some embodiments, passivevalve 515 is at least twenty five microns thick and not more than fiftymicrons thick. In an alternate embodiment, valve 515 might be an activevalve, for example analogous to valve 315.

In addition, cooling cell 510 includes valve 580 for orifice plate 520.Valve 580 is an active valve. In the embodiment shown, valve 580 is apiezoelectric valve element including substrate 581, piezoelectric 583and electrode 582 having apertures 584 therein. Thus, valve 580 may beanalogous to piezoelectric cooling element 510 and/or valve 515. In someembodiments, valve 580 is at least fifty and not more than fifty micronsthick. Valve 580 may be affixed to orifice plate 520, for example via anadhesive such as epoxy applied near the perimeter. Leads 585 and 586 areused to actuate valve 580. Valve 580 selectively allows fluid to flowthrough orifices 522 in orifice plate.

In operation, piezoelectric cooling system 500 functions in a manneranalogous to cooling systems 100, 200 and 300. Piezoelectric coolingelement 510 is actuated to move away from structure 530 and, therefore,valve 515. Fluid flows through apertures 514. During this time, valve580 is actuated to remain in contact with orifice plate 520. Thus, theflow fluid from the region between orifice plate 520 and structure 530into the chamber formed between orifice plate 520 and cooling element510 may be reduced or prevented. In the embodiment shown, apertures 584are aligned with some orifices 522 when valve 580 is in contact withorifice plate 520. In such an embodiment, some fluid may return to thechamber when piezoelectric cooling element 510 is actuated to move (e.g.deform) away from orifice plate 520. In other embodiments, apertures 584are aligned with sections of orifice plate 520 that are free of orificeswhen valve 580 is in contact with orifice plate 520. In suchembodiments, fluid may be substantially prevented from returning viaorifices 522 when piezoelectric cooling element 510 is actuated todeform away from orifice plate 520 and structure 530. Piezoelectriccooling element 510 is activated to move toward structure 530.Piezoelectric cooling element 510 thus pushes fluid in the chamberbetween element 510 and orifice plate 520 toward structure 530. Duringthis motion, valve 580 is actuated to move away from orifice plate 520,allowing fluid pass more readily through apertures 584 to reach orifices522. The fluid moves through orifices 522 and in jets toward structure530, in a manner analogous to that described above for other coolingsystems. FIG. 5B is a graph 590 depicting an exemplary embodiment of themotion of cooling element 510, while FIG. 5C is a graph 592 depicting anexemplary embodiment of the motion of valve 580. Thus, components 580and 510 are out of phase. Both components 510 and 580 may be vibrated atthe same ultrasonic frequency described above. In addition, bothcomponents 510 and 580 may be vibrated at or near resonance frequencies.Further, the amplitude of motion of cooling element 510 is generallydesired to be larger in amplitude than the motion of valve 580.

Piezoelectric cooling system 500 may more efficiently dissipate heatfrom structure 530. Because structure 530 is more efficiently cooled,structure 530 may be run at higher speed and/or power for longer times.Thus, performance of a device utilizing structure 530 may be improved.Further, cooling system 500 is a MEMS device having the dimensionsdescribed above. Thus, piezoelectric cooling system 500 is suitable foruse in mobile devices, such as smart phones, in which limited space isavailable. Piezoelectric cooling system 500 may also be used in othercompute devices-both mobile and non-mobile. Performance of such devicesmay thus be improved. Because piezoelectric cooling elements 510 may bevibrated at ultrasonic frequencies and/or at or near resonance,piezoelectric cooling system 500 may be quieter and consume less power.Further, use of valve 580 may prevent or reduce the back flow of heatedfluid from the region close to structure 530 through the orifices 522.This fluid may instead move through chimneys 540 to be cooled.Efficiency of the cooling system 500 may thereby be enhanced. Thus, thebenefits of improved, quiet cooling may be achieved with limitedadditional power. Consequently, performance of devices incorporatingcooling system 500 may be improved.

FIG. 6 is a diagram depicting an exemplary embodiment of a piezoelectriccooling system 600. For clarity, only certain components are shown andFIG. 6 is not to scale. Piezoelectric cooling system 600 is used inconnection with a structure 630 and includes a cell 601. Structure 630generates heat during operation and is desired to be cooled. Structure630 is analogous to structure 130. Piezoelectric cooling system 600 mayfit within mobile computing devices and is a MEMS cooling device.Piezoelectric cooling system 600 may also be viewed as a single cell ina larger cooling system that may include multiple cells/piezoelectriccooling systems 600. Also shown in FIG. 6 is plate 650 which may be partof the device, such as a smart phone, in which piezoelectric coolingsystem 600 resides. However, plate 650 might be replaced with anothercomponent.

Piezoelectric cooling system 600 includes piezoelectric cooling element610 that is analogous to previously discussed piezoelectric coolingelements and valve 615 that is analogous to valve 215. Piezoelectriccooling element 610 thus includes substrate 611, piezoelectric layer 612and electrode 613 having apertures 614 that are offset from the center.Also shown are chimneys 640, spacers 641, 642 and 643. Similarly, valve615 includes substrate 616, piezoelectric layer 617 and electrode 618.For simplicity, leads to cooling element 610 are not shown.

Although piezoelectric cooling element 610 is present, it is closer tostructure 630. In some embodiments, piezoelectric cooling element 610 isat or near the location where the orifice plate would otherwise be.Similarly, top plate 690 is at or near the location where the coolingelement, such as cooling element 210, would be in other embodiments. Topplate 690 includes aperture 692. Also shown is valve 694. In anotherembodiment, valve 694 may be omitted and/or aperture 692 may be locatednear the edges of plate 690. In some embodiments, plate 690 may bereplaced by a piezoelectric cooling element and valve such as components210 and 215 or 310 and 315.

Piezoelectric cooling system 600 may be a MEMS device and thus may havedimensions analogous to those described above. Piezoelectric coolingsystem 600 is similar to other piezoelectric cooling systems describedherein. However, cooling element 610 has replaced an orifice plate andtop plate 690 has replaced cooling element 610.

In operation, cooling element 610 is actuated to move away fromstructure 630 and valve 615 is actuated to open apertures 614. Fluidflows from the distal to the proximal side of cooling element 610 andmoves toward structure 630 in jets. When cooling elements 610 is drivento move toward structure 630, valve 615 is actuated so that apertures614 remain closed. However, valve 694 opens aperture 692. Fluid flowsthrough plate 690 into the chamber formed by plate 690 and coolingelement 610.

Piezoelectric cooling system 600 may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem may more efficiently dissipate heat from structure 630, allowingstructure 630 to be run at higher speed and/or power for longer times.Thus, performance of a device utilizing structure 630 may be improved.Further, cooling system 600 is a MEMS device having the dimensionsdescribed above. Thus, piezoelectric cooling system 600 is suitable foruse in mobile devices, such as smart phones, in which limited space isavailable. Piezoelectric cooling system 600 may also be used in othercompute devices-both mobile and non-mobile. Performance of such devicesmay thus be improved. Because piezoelectric cooling elements 610 may bevibrated at ultrasonic frequencies and/or at or near resonance,piezoelectric cooling system 600 may be quieter and consume less power.Thus, the benefits of improved, quiet cooling may be achieved withlimited additional power. Consequently, performance of devicesincorporating cooling system 600 may be improved.

FIG. 7 is a diagram depicting an exemplary embodiment of a piezoelectriccooling system 700A. For clarity, only certain components are shown andFIG. 7 is not to scale. Piezoelectric cooling system 700 is used inconnection with a structure (not shown) and includes a cell 701A.Piezoelectric cooling system 700A may fit within mobile computingdevices and is a MEMS cooling device. Piezoelectric cooling system 700Amight also be used in non-mobile devices. Although rear spacers andfront spacers to the structure are not shown, such components aregenerally present. Piezoelectric cooling system 700A may also be viewedas a single cell in a larger cooling system that may include multiplecells/piezoelectric cooling systems 700A.

Piezoelectric cooling system 700A includes piezoelectric cooling element710A that is generally analogous to previously discussed piezoelectriccooling elements but does not have an entry path to allow fluid to passthrough cooling element 710A. Thus, piezoelectric cooling element 710Aincludes substrate 711, piezoelectric layer 712 and electrode 713. Forsimplicity, leads to cooling element 710A and are not shown. Also shownis orifice plate 720 having orifices 722. Piezoelectric cooling system700A may be a MEMS device and thus may have dimensions analogous tothose described above. Piezoelectric cooling system 700A is similar toother piezoelectric cooling systems described herein. However, coolingelement 710A does not move fluid through cooling element 710A. Thus, noapertures are present in cooling element 710A and no valve is used.

In operation, cooling element 710A is actuated to move away from orificeplate 720. Fluid flows in through apertures 722 or other orifice in thechamber formed by cooling element 710A and orifice plate 720. Whencooling elements 710A is driven to move toward orifice plate 620, fluidis moved toward orifice plate 720 and through apertures 722 at speedsdescribed above. Piezoelectric cooling element 700A thus macroscopicallymoves fluid, such as a gas (e.g. air). For example, piezoelectriccooling element 700 may be capable of generating fluid speeds in excessof thirty meters per second. Arrows in FIG. 7 depict the direction ofmotion of fluid from orifices 722. In the embodiment shown, anystructures (not shown) proximate to orifice plate 720 are generallyspaced further away than fifty microns to prevent movement hot fluidadjacent to the structure from being drawn back through orifices 722. Insome embodiments, structures may be adjacent to spacers 742. A channelsubstantially parallel to the direction of fluid flow may be present. Insuch embodiments, fluid may be more effectively moved by cooling system700.

Piezoelectric cooling system 700A may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem 700A may move fluid at speeds of fifty meters per second orabove. Further, cooling system 700A is a MEMS device having thedimensions described above. Thus, piezoelectric cooling system 700A issuitable for use in mobile devices, such as smart phones, in whichlimited space is available. Performance of such devices may thus beimproved. Because piezoelectric cooling elements 710A may be vibrated atultrasonic frequencies and/or at or near resonance, piezoelectriccooling system 700A may be quieter and consume less power. Thus, thebenefits of improved, quiet cooling may be achieved with limitedadditional power. Consequently, performance of devices incorporatingcooling system 700A may be improved.

FIGS. 8A-8E are diagrams depicting exemplary embodiments 700B and 700Cof a piezoelectric cooling system usable with a structure. Piezoelectriccooling systems 700B and 700C utilize two stage movement. For clarity,only certain components are shown and FIGS. 8A-8E are not to scale.Piezoelectric cooling systems 700B and 700C are used in connection witha structure (not shown). Piezoelectric cooling systems 700B and 700C mayfit within mobile computing devices and is a MEMS cooling device.Although rear spacers and front spacers to the structure are not shown,such components are generally present. Each piezoelectric cooling system700B and 700C may also be viewed as a single cell in a larger coolingsystem that may include multiple cells/piezoelectric cooling systems700B and 700C.

FIGS. 8A-8C depict one piezoelectric cooling system 700B including atleast one cell 701B. Piezoelectric cooling system 700B includespiezoelectric cooling element 710B that is generally analogous topreviously discussed piezoelectric cooling elements but does not have anentry path to allow fluid to pass through cooling element 710B in someembodiments. Thus, piezoelectric cooling element 710B includes substrate711, piezoelectric layer 712 and electrode 713. For simplicity, leads tocooling element 710B and are not shown. Also shown is orifice plate 720having orifices 722. Piezoelectric cooling system 700B may be a MEMSdevice and thus may have dimensions analogous to those described above.Piezoelectric cooling system 700B is similar to other piezoelectriccooling systems described herein. Also depicted is active valve 780 thatis analogous to active vale 580. Active valve 780 includes substrate781, piezoelectric 782 and electrode 783 that are analogous to substrate581, piezoelectric 582 and electrode 583. However, additionalpiezoelectric elements 715B and chamber walls 790B are shown. In theembodiment shown, chamber walls 790B are connected to or part of thesame piece as substrate 711. For example, chamber walls 790B may bestainless steel and/or Hastelloy. Piezoelectric elements 715B includesubstrate 716, piezoelectric 717 and electrode 718 that are analogous tosubstrate 711, piezoelectric 712 and electrode 713, respectively. Thus,piezoelectric elements 715B may be seen as forming cantilevered sectionscoupled between piezoelectric cooling element 710B/chamber walls 790Band spacers 742. Piezoelectric elements 715B also include apertures 719therein. For simplicity, the components of only one piezoelectricelement 715B are labeled. Further, for clarity, some components are notlabeled in FIGS. 8B and 8C.

Piezoelectric cooling system 700B utilizes two-step motion for drivingfluid. This may be seen in FIGS. 8B and 8C. In operation, piezoelectricelements 715B are actuated to vibrate toward and away from orifice plate720. This moves piezoelectric cooling element 710B and chamber walls 790be toward and away from orifice plate 720. Piezoelectric cooling element710B is also actuated to vibrate toward and away from orifice plate 720.FIG. 8B depicts piezoelectric cooling system 700B after bothpiezoelectric elements 715B and piezoelectric cooling element 710B aredriven. At the time shown in FIG. 8B, piezoelectric cooling element 710Bis moved from orifice plate 720 by the piezoelectric elements 715B. Insome embodiments, piezoelectric cooling element 710B is also deformed toflex away from orifice plate 720. Chamber walls 790B have thus movedaway from orifice plate 720. Active valve 780 is also actuated such thatfluid does not flow through orifices 722 from closer to the structure(not shown) being cooled. Fluid from the distal side of piezoelectriccooling element 710B (and the distal side of piezoelectric elements715B) flows in through apertures 719 or other orifice(s) and betweenchamber walls 790B. This fluid flow is shown by arrows in FIG. 8B.

FIG. 8C depicts piezoelectric cooling cell 700B when piezoelectricelements 715 are actuated to move chamber walls 790B/element 710B towardorifice plate 720 and piezoelectric cooling element 710B is activated tovibrate towards orifice plate 720. In addition, valve 780 is actuated tomove away from orifice plate 720. Consequently, fluid is moved towardorifice plate 720 and through apertures 722 at speeds described above.The fluid flow is shown by arrows in FIG. 8C. Because chamber walls 790Bare in contact with valve 780, fluid does not move back throughapertures 719. In some embodiments, a passive or active valve may beprovided such that apertures 719 are closed by the valve in thesituation shown in FIG. 8C. This may be used in addition to or in lieuof the chamber walls 790B contacting valve 780 to prevent back flow offluid through apertures 719. Thus, piezoelectric cooling element 710B incombination with piezoelectric elements 715B move fluid from the distalto the proximal side of piezoelectric cooling element 710B and drive thefluid through orifices in orifice plate 720. As such, piezoelectriccooling element 710B can be considered to be configured to direct thefluid from the distal side to the proximal side of piezoelectric coolingelement 710B such that the fluid moves in a direction that is incidenton a surface of a heat-generating structure (not shown in FIGS. 8A-8C)at a substantially perpendicular angle and then is deflected to movealong the surface of the heat-generating structure to extract heat fromthe heat-generating structure.

Piezoelectric cooling system 700B may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem 700B may more efficiently dissipate heat from a structure (notshown). Piezoelectric cooling system 700B may move fluid at speeds of atleast thirty meters per second, at least fifty meters per second orabove. Further, cooling system 700B is a MEMS device having thedimensions described above. Thus, piezoelectric cooling system 700B issuitable for use in mobile devices, such as smart phones, in whichlimited space is available. Piezoelectric cooling system 700B may alsobe used in other compute devices-both mobile and non-mobile. Performanceof such devices may thus be improved. Because piezoelectric coolingelements 710B may be vibrated at ultrasonic frequencies and/or at ornear resonance, piezoelectric cooling system 700B may be quieter andconsume less power. Thus, the benefits of improved, quiet cooling may beachieved with limited additional power. Consequently, performance ofdevices incorporating cooling system 700B may be improved.

FIGS. 8D-8E depict another embodiment of piezoelectric cooling system700C including at least one cell 701C. Piezoelectric cooling system 700Cincludes piezoelectric cooling element 710C that is generally analogousto previously discussed piezoelectric cooling elements but does not havean entry path to allow fluid to pass through cooling element 710C insome embodiments. Thus, piezoelectric cooling element 710C includessubstrate 711, piezoelectric layer 712 and electrode 713. Forsimplicity, leads to cooling element 710A and are not shown. Also shownis orifice plate 720 having orifices 722. Piezoelectric cooling system700C may be a MEMS device and thus may have dimensions analogous tothose described above. Piezoelectric cooling system 700C is similar toother piezoelectric cooling systems described herein. Also depicted isactive valve 780 that is analogous to active vale 580. Active valve 780includes substrate 781, piezoelectric 782 and electrode 783 that areanalogous to substrate 581, piezoelectric 582 and electrode 583.Additional piezoelectric elements 715C and chamber walls 790C are shown.In the embodiment shown, chamber walls 790B are connected to but notpart of the same piece as substrate 711. Chamber walls 790C may still bestainless steel and/or Hastelloy. Piezoelectric elements 715C includesubstrate 716, piezoelectric 717 and electrode 718 that are analogous tosubstrate 711, piezoelectric 712 and electrode 713, respectively. Thus,piezoelectric elements 715C may be seen as forming cantilevered sectionscoupled between piezoelectric cooling element 710C/chamber walls 790Cand spacers 742. Although four piezoelectric elements 715C are shown,another number may be used in other embodiments. Piezoelectric elements715C are not shown as including apertures. Instead, piezoelectricelements 715C are cantilevered strips separated by spaces.

Piezoelectric cooling system 700C operates in an analogous manner topiezoelectric cooling system 700B. Thus, piezoelectric elements 715C and710C, as well as active valve 780 are driven. Thus, fluid from thedistal side of piezoelectric elements 710C and 715C moves through spacesbetween piezoelectric elements 715C to the proximal side ofpiezoelectric cooling element 710C. Fluid is then driven throughorifices 722 of orifice plate 720. Thus, piezoelectric cooling element710C in combination with piezoelectric elements 715C move fluid from thedistal to the proximal side of piezoelectric cooling element 710C anddrive the fluid through orifices in orifice plate 720. As such,piezoelectric cooling element 710C can be considered to be configured todirect the fluid from the distal side to the proximal side ofpiezoelectric cooling element 710C such that the fluid moves in adirection that is incident on a surface of a heat-generating structure(not shown in FIGS. 8D-8E) at a substantially perpendicular angle andthen is deflected to move along the surface of the heat-generatingstructure to extract heat from the heat-generating structure.

Piezoelectric cooling system 700C may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem 700C may more efficiently dissipate heat from a structure (notshown). Piezoelectric cooling system 700C may move fluid at speeds of atleast thirty meters per second, at least fifty meters per second orabove. Further, cooling system 700C is a MEMS device having thedimensions described above. Thus, piezoelectric cooling system 700C issuitable for use in mobile devices, such as smart phones, in whichlimited space is available. Piezoelectric cooling system 700C may alsobe used in other compute devices-both mobile and non-mobile. Performanceof such devices may thus be improved. Because piezoelectric coolingelements 700C may be vibrated at ultrasonic frequencies and/or at ornear resonance, piezoelectric cooling system 700C may be quieter andconsume less power. Thus, the benefits of improved, quiet cooling may beachieved with limited additional power. Consequently, performance ofdevices incorporating cooling system 700C may be improved.

FIGS. 9A-9C depict another embodiment of a piezoelectric cooling system700D including at least one cell 701D. For clarity, not all componentsare depicted and FIGS. 9A-9C are not to scale. Piezoelectric coolingsystem 700D includes piezoelectric cooling element 710D that isgenerally analogous to previously discussed piezoelectric coolingelements but does not have an entry path to allow fluid to pass throughcooling element 710D in some embodiments. Thus, piezoelectric coolingelement 710D includes substrate 711, piezoelectric layer 712 andelectrode 713. For simplicity, leads to cooling element 710D and are notshown. Also shown is orifice plate 720 having orifices 722.Piezoelectric cooling system 700D may be a MEMS device and thus may havedimensions analogous to those described above. Piezoelectric coolingsystem 700D is similar to other piezoelectric cooling systems describedherein. Also depicted is active valve 780 that is analogous to activevale 580. Active valve 780 includes substrate 781, piezoelectric 782 andelectrode 783 that are analogous to substrate 581, piezoelectric 582 andelectrode 583. However, additional piezoelectric elements 715B andchamber walls 790D are shown. In the embodiment shown, chamber walls790B are connected to orifice plate 720. Thus, chamber walls 790C aresubstantially stationary. In the embodiment shown, piezoelectric elementcomponents 712 and 713 are not shown as extending to spacers 742 orapertures 719. In other embodiments, components 712 and/or 713 mayextend to/past apertures 719 and/or to spacer 742.

Piezoelectric cooling system 700D operates in an analogous manner topiezoelectric cooling system 700B and 700C. However, in the embodimentshown, one-step motion may be used. Thus, piezoelectric elements 715Band/or 715C may be omitted in some embodiments. Thus, piezoelectricelement 710D, as well as active valve 780 are driven. This can be seenin FIGS. 9B and 9C. For clarity, not all components are labeled in FIGS.9B and 9C. Piezoelectric cooling element 710D is also actuated tovibrate toward and away from orifice plate 720. FIG. 9B depictspiezoelectric cooling system 700D after piezoelectric cooling element710D is driven. At the time shown in FIG. 9B, piezoelectric coolingelement 710D is deformed to flex away from orifice plate 720 and chamberwalls 790D. Active valve 780 is also actuated such that fluid does notflow through orifices 722 from closer to the structure (not shown) beingcooled. Fluid from the distal side of piezoelectric cooling element 710Dflows in through apertures 719 or other orifice(s) and between chamberwalls 790D. This fluid flow is shown by arrows in FIG. 9B.

FIG. 9C depicts piezoelectric cooling cell 700D when activated tovibrate towards orifice plate 720. In addition, valve 780 is actuated tomove away from orifice plate 720. Consequently, fluid is moved towardorifice plate 720 and through apertures 722 at speeds described above.The fluid flow is shown by arrows in FIG. 9C. Because chamber walls 790Dare in contact with piezoelectric cooling element 720D, fluid does notmove back through apertures 719.

Piezoelectric cooling system 700D may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem 700D may more efficiently dissipate heat from a structure (notshown). Piezoelectric cooling system 700D may move fluid at speeds of atleast thirty meters per second, at least fifty meters per second orabove. Further, cooling system 700D is a MEMS device having thedimensions described above. Thus, piezoelectric cooling system 700D issuitable for use in mobile devices, such as smart phones, in whichlimited space is available. Piezoelectric cooling system 700D may alsobe used in other compute devices-both mobile and non-mobile. Performanceof such devices may thus be improved. Because piezoelectric coolingelements 700D may be vibrated at ultrasonic frequencies and/or at ornear resonance, piezoelectric cooling system 700D may be quieter andconsume less power. Thus, the benefits of improved, quiet cooling may beachieved with limited additional power. Consequently, performance ofdevices incorporating cooling system 700D may be improved.

FIGS. 10A-10C are diagrams depicting another exemplary embodiment of apiezoelectric cooling system 700E usable with a structure and includingat least one cell 701E. For clarity, only certain components are shownand FIGS. 10A-10C are not to scale. Piezoelectric cooling system 700Eincludes piezoelectric cooling element 710E that is generally analogousto previously discussed piezoelectric cooling elements but does not havean entry path to allow fluid to pass through cooling element 710E insome embodiments. Thus, piezoelectric cooling element 710E includessubstrate 711E, piezoelectric layer 712E and electrode 713E. Forsimplicity, leads to cooling element 710E and are not shown. Also shownis orifice plate 720 having orifices 722. Piezoelectric cooling system700E may be a MEMS device and thus may have dimensions analogous tothose described above. Piezoelectric cooling system 700E is similar toother piezoelectric cooling systems described herein. Further, elements792 and 794 are shown. Element 792 may be similar to substrate 711E andincludes aperture 793 therein. Element 792 may be similar to substrate711E and includes apertures 795 therein. In other embodiments, othernumbers of apertures may be used in this and other embodiments. Thechamber which drives fluid through orifices 722 is formed by elements792 and 794. Also shown are plugs 715E on piezoelectric cooling element710E, which are substantially aligned with apertures 795.

Piezoelectric cooling system 700E operates in an analogous manner toother piezoelectric cooling systems disclosed herein. However,piezoelectric cooling element 710E undergoes tensile and compressivemotion. Thus, the direction(s) of vibration is substantiallyperpendicular to the vibration direction described previously. Inoperation, piezoelectric element 710E is driven. Piezoelectric coolingelement 710E is actuated to compress and stretch substantially along thesurface of orifice plate 720. This is shown by the two-headed arrow inFIG. 10A and the arrows in FIGS. 10B and 10C. FIG. 10B depictspiezoelectric cooling system 700E after piezoelectric cooling element710E is driven to be compressed. Consequently, elements 792 and 794deform away from piezoelectric cooling element 710E. Element 792contacts orifice plate 720, preventing or reducing backflow of fluidthrough orifices 722. To this extent, element 792 also acts as a valve.Element 794 draws outside fluid through apertures 795. Fluid also flowsthrough aperture 714, from the distal side to the proximal side ofpiezoelectric cooling element 710E. Thus, the chamber formed by elements792 and 794 takes in fluid. Fluid flow is indicated by arrows in FIG.10B.

FIG. 10C depicts piezoelectric cooling system 700E when piezoelectriccooling element 710E is under tensile strain. Thus, piezoelectriccooling element 710E stretches and elements 792 and 794 move towardpiezoelectric cooling element 710E. Apertures 795 contact plugs 715Eand/or piezoelectric cooling element 710E. Consequently, outflow offluid from apertures 795 may be prevented or reduced. Thus, plugs 715Eand/or piezoelectric cooling element 710E may also function as a valve.Fluid flows through aperture 793 and orifices 792. Fluid flow isindicated by arrows in FIG. 10C. Thus, piezoelectric cooling element710E in combination with elements 792 and 794 move fluid from the distalto the proximal side of piezoelectric cooling element 710E and drive thefluid through orifices in orifice plate 720. As such, piezoelectriccooling element 710E can be considered to be configured to direct thefluid from the distal side to the proximal side of piezoelectric coolingelement 710E such that the fluid moves in a direction that is incidenton a surface of a heat-generating structure (not shown in FIGS. 10A-10C)at a substantially perpendicular angle and then is deflected to movealong the surface of the heat-generating structure to extract heat fromthe heat-generating structure.

Piezoelectric cooling system 700E may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem 700E may more efficiently dissipate heat from a structure (notshown). Piezoelectric cooling system 700D may move fluid at speeds of atleast thirty meters per second, at least fifty meters per second orabove. Further, cooling system 700E is a MEMS device having thedimensions described above. Thus, piezoelectric cooling system 700E issuitable for use in mobile devices, such as smart phones, in whichlimited space is available. Piezoelectric cooling system 700E may alsobe used in other compute devices-both mobile and non-mobile. Performanceof such devices may thus be improved. Because piezoelectric coolingelements 700E may be vibrated at ultrasonic frequencies and/or at ornear resonance, piezoelectric cooling system 700E may be quieter andconsume less power. Thus, the benefits of improved, quiet cooling may beachieved with limited additional power. Further, an active valve nearorifice plate 720 may be omitted. Consequently, performance of devicesincorporating cooling system 700E may be improved.

FIG. 11 is a diagram depicting an exemplary embodiment of piezoelectriccooling system 800. For clarity, only certain components are shown andFIG. 11 is not to scale. Piezoelectric cooling system 800 is used inconnection with a structure (not shown) to be cooled and includes a cell801. Piezoelectric cooling system 800 may fit within mobile computingdevices and is a MEMS cooling device. Piezoelectric cooling system 800may also be viewed as a single cell in a larger cooling system that mayinclude multiple cells/piezoelectric cooling systems 800.

Piezoelectric cooling system 800 includes piezoelectric cooling element810, orifice plate 820, active valve 815 and valve 880 that areanalogous to previously described cooling elements, orifice plates,active valves and valve(s), respectively. Piezoelectric cooling element810 thus includes substrate 811, piezoelectric layer 812 and electrode813 having apertures 814 that are offset from the center. Similarly,valve 815 includes substrate 816, piezoelectric layer 817 and electrode818. Active valve 880 includes substrate 881, piezoelectric layer 882and electrode 883 having apertures 884 therein. For simplicity, leadsare not shown. Also shown are spacers 842 and 843 that are analogous topreviously described spacers that are similarly located. Although notshown, chimneys adjacent to cell 801 and that are analogous topreviously described chimneys may be present. Thus, piezoelectriccooling system 800 is most analogous to piezoelectric cooling system500. However, active valve 815 is present instead of passive valve 515.In other embodiments, a passive valve may be used instead of activevalve 815.

Piezoelectric cooling system 800 may be a MEMS device and thus may havedimensions analogous to those described above. Piezoelectric coolingsystem 800 is similar to other piezoelectric cooling systems describedherein. However, the orientation of piezoelectric cooling system 800with respect to the top of the page has changed. This indicates that oneor more of the piezoelectric cooling systems described herein may beoriented in other manners than shown in FIGS. 1A-20B. For example, inaddition to piezoelectric cooling system 800, other piezoelectriccooling systems described herein may be used to drive macroscopic fluidflow through a device, across components of the device such that theflow is substantially parallel to a top surface of the device.Piezoelectric cooling system 800 may thus be used to cool verticalstructures and/or provide macroscopic motion of a fluid, such as air.

In operation, cooling element 810 is actuated to vibrate. Valve 815 isactuated such that fluid flows through apertures 814 and 819 from thedistal to the proximal side of cooling element 810 during motion ofcooling element 810 away from orifice plate 820. Similarly valve 880 isactuated to close most or all of orifices 822 during motion of coolingelement 810 away from orifice plate 820. Thus, drawing in of fluidthrough orifices 822 is reduced or eliminated. During motion of coolingelement 810 toward orifice plate 820, valve 815 is actuated to closeapertures 814. In contrast, valve 880 is actuated to move away fromorifice plate 820 so that fluid has a path through apertures 884 andorifices 822. Thus, cooling element 810 pushes fluid through orifices injets.

Piezoelectric cooling system 800 may share the benefits of otherpiezoelectric cooling systems described herein. Piezoelectric coolingsystem may more efficiently dissipate heat from a structure, allowingfor higher clock speeds and/or power for longer times. Thus, performanceof a device utilizing cooling system 800 may be improved. Further,piezoelectric cooling system 800 is a MEMS device having the dimensionsdescribed above. Thus, piezoelectric cooling system 800 is suitable foruse in mobile devices, such as smart phones, in which limited space isavailable. Piezoelectric cooling system 800 may also be used in othercompute devices-both mobile and non-mobile. Performance of such devicesmay thus be improved. Because piezoelectric cooling elements 810 may bevibrated at ultrasonic frequencies and/or at or near resonance,piezoelectric cooling system 800 may be quieter and consume less power.Thus, the benefits of improved, quiet cooling may be achieved withlimited additional power. Consequently, performance of devicesincorporating cooling system 800 may be improved.

FIGS. 12A, 12B, 12C and 12D are diagrams depicting exemplary embodimentsof piezoelectric cooling systems 900A, 900B, 900C and 900D,respectively. For clarity, only certain components are shown and FIGS.12A-12D are not to scale. Cooling systems 900A, 900B, 900C and 900D areused in connection with a structure (not shown) analogous to structuresdescribed above. Cooling systems 900A, 900B, 900C and 900D may be MEMSsystems having dimensions in the ranges described above and in proximityto the structures desired to be cooled as described above.

FIG. 12A depicts piezoelectric cooling system 900A including cell 901Ahaving cooling element 910 and orifice plate 920A having apertures 922Athat are analogous to cells, piezoelectric cooling elements, and orificeplates having apertures described above. For simplicity, valve andapertures in cooling element 910 are not shown. A return path that mayexist outside of cell 901A is not shown for simplicity. Piezoelectriccooling system 900A operates in an analogous manner to piezoelectriccooling systems described above. In the embodiment shown in FIG. 12A,orifices 922A are oriented substantially perpendicular to the surface oforifice plate 920A. Although shown as having constant diameter, orifices922A may have a diameter or shape that changes through orifice plate920A.

FIG. 12B depicts piezoelectric cooling system 900B including cell 901Bhaving cooling element 910 and orifice plate 920B having apertures 922Bthat are analogous to cells, piezoelectric cooling elements, and orificeplates having apertures described above. For simplicity, valve andapertures in cooling element 910 are not shown. A return path that mayexist outside of cell 901B is not shown for simplicity. Piezoelectriccooling system 900B operates in an analogous manner to piezoelectriccooling systems described above. In the embodiment shown in FIG. 12B,orifices 922B are oriented at either substantially perpendicular to thesurface of orifice plate 920B (the central orifice) or at a nonzeroacute angle from normal to the surface of orifice plate 920B. Inparticular, orifices 922B are generally oriented toward the edges ofcell 901B. Although shown as having constant diameter, orifices 922B mayhave a diameter or shape that changes through orifice plate 920B.

FIG. 12C depicts piezoelectric cooling system 900C including cell 901Chaving cooling element 910 and orifice plate 920C having apertures 922Cthat are analogous to cells, piezoelectric cooling elements, and orificeplates having apertures described above. For simplicity, valve andapertures in cooling element 910 are not shown. A return path that mayexist outside of cell 901C is not shown for simplicity. Piezoelectriccooling system 900C operates in an analogous manner to piezoelectriccooling systems described above. In the embodiment shown in FIG. 12C,orifices 922C are oriented at either substantially perpendicular to thesurface of orifice plate 920C (the central orifice) or at a nonzeroacute angle from normal to the surface of orifice plate 920C. Inparticular, orifices 922C are generally oriented toward the center ofcell 901C. Although shown as having constant diameter, orifices 922C mayhave a diameter or shape that changes through orifice plate 920C.

FIG. 12D depicts piezoelectric cooling system 900D including cell 901Dhaving cooling element 910 and orifice plate 920D having apertures 922Dthat are analogous to cells, piezoelectric cooling elements, and orificeplates having apertures described above. For simplicity, valve andapertures in cooling element 910 are not shown. A return path that mayexist outside of cell 901D is not shown for simplicity. Piezoelectriccooling system 900D operates in an analogous manner to piezoelectriccooling systems described above. In the embodiment shown in FIG. 12D,orifices 922D are oriented substantially perpendicular to the surface oforifice plate 920D, but have different diameters or shapes. For example,in some embodiments, the orifice diameter decreases with increasingdistance from the center of orifice plate 920D (decreasing distance tothe edge of orifice plate 920D). In other embodiments, orifice diameterincreases with increasing distance from the center of orifice plate920D. Other arrangements of diameters are possible.

Piezoelectric cooling systems 900A, 900B, 900C and 900D share thebenefits of the piezoelectric cooling systems described herein. Thus,efficient, quite cooling using high speed fluid flows may be provided.In addition, because of the configurations of orifices 922A, 922B, 922Cand 922D, the flow through orifices 922A, 922B, 922C and 922D, as wellas the jets formed may be tailored. Consequently, performance may befurther enhanced.

FIGS. 13A, 13B, 13C, 13D and 13E are diagrams depicting exemplaryembodiments of orifice plates 1020A, 1020B, 1020C, 1020D and 1020E,respectively. For clarity, only certain components are shown and FIGS.13A-13E are not to scale. Orifice plates 1020A, 1020B, 1020C, 1020D and1020E include orifices 1022A, 1022B, 1022C, 1022D and 1022E,respectively. Orifice plates 1020A, 1020B, 1020C, 1020D and 1020E areused in connection with piezoelectric cooling systems analogous to thosedescribed above. Thus, orifice plates 1020A, 1020B, 1020C, 1020D and1020E and orifices 1022A, 1022B, 1022C, 1022D and 1020E may be MEMScomponents having dimensions in the ranges described above. Orificeplate 1020A includes orifices arranged in a hexagonal close-packedarray. Other close packed arrays may also be used. Orifice plate 1020Bincludes orifices 1022B arranged in a rectangular array. Orifice plate1020C include orifices 1022C arranged such that the orifice density ishigher closer to the center of plate 1020C. Orifice plate 1020D includesorifices 1022D arranged such that the orifice density is higher closerto the edges of orifice plate 1020D. Orifice plate 1020E includesorifices 1022E and regions 1023 (indicated by dotted lines). Regions1023 are configured to be aligned with apertures in a valve, such asapertures 584 in valve 580. Orifices 1022E are arranged such thatregions 1023 are free of orifices. Consequently, orifice plate 1020E maymore effectively prevent heated fluid from returning through orifices1022E when piezoelectric cooling element (not shown in FIG. 13E) isdriven to move (e.g. deform) away from orifice plate 1020E. Otherarrangements are possible. Further, orifices 1022A, 1022B, 1022C, 1022Dand 1022E are shown as having a constant diameter. In other embodiments,the diameter, shape and angle perpendicular to the page may vary. Thus,piezoelectric cooling systems using orifice plates 1020A, 1020B, 1020Cand 1020D not only share the benefits of the piezoelectric coolingsystems described herein, but also may tailor the jets formed using theconfiguration of orifices 1022A, 1022B, 1022C and 1022D, respectively.Consequently, performance may be further enhanced.

FIGS. 14A-14D are diagrams depicting exemplary embodiments of coolingsystems 1100A, 1100B, 1100C and 1100D usable with a heat-generatingstructure. For clarity, only certain components are shown and FIGS.14A-14D are not to scale. Cooling systems 1100A, 1100B, 1100C and 1100Dare used in connection with a structure 1130 analogous to structure 130and 230. Structure 1130 generates heat during operation and is desiredto be cooled. Cooling systems 1100A, 1100B, 1100C and 1100D may be MEMSsystems having dimensions in the ranges described above.

FIG. 14A depicts piezoelectric cooling system 1100A having cells on bothside of structure 1130. Thus, piezoelectric cooling system 1100Aincludes cells 1101 and 1101A, cooling elements 1110 and 1110A, andorifice plates 1120 and 1120A having apertures 1122 and 1122A that areanalogous to cells, piezoelectric cooling elements, and orifice plateshaving apertures described herein. Orifice plates 1120 and 1120A arealso shown as including chimneys/return paths 1140 and 1140A,respectively, that are analogous to chimneys/return paths 240. Further,some of orifices 1122 and 1122A are at a nonzero acute angle, θ, withrespect to normal to the surface of structure 1130. In the embodimentshown, orifices 1140 and 1140A are either vertical or angled toward theedges of each cell 1101 and 1101A, respectively.

Piezoelectric cooling system 1100A operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1100A may more efficiently and quietly cool structure1130 at lower power. Further, piezoelectric cooling system coolsstructure 1130 at multiple surfaces. As a result, performance may befurther improved.

FIG. 14B depicts piezoelectric cooling system 1100B. Piezoelectriccooling system 1100B includes cells 1101B, cooling elements 1110B, andorifice plate 1120B having apertures 1122B that are analogous to cellsand their components described herein. Piezoelectric cooling system1100B operates in an analogous manner to piezoelectric cooling systemsdescribed herein. Also shown is return path 1140 for fluid to returnfrom the proximal to the distal sides of piezoelectric cooling elements1110B. Also shown is entry path 1112 that allows fluid to flow from thedistal to the proximal side of piezoelectric cooling elements 1110B whenfluid is not being pushed through apertures 1122. In some embodiments,entry path 1112 functions in a manner analogous to valve 215. Forexample, entry path 1112 may actively or passively control fluid flowfrom the distal to the proximal side of piezoelectric cooling element1110B. In other embodiments, entry path may function in a differentmanner and/or be located at a different portion of piezoelectric coolingelements 1110B.

Piezoelectric cooling system 1100B operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1100B may more efficiently and quietly cool structure1130 at lower power.

FIG. 14C depicts piezoelectric cooling system 1100C. Piezoelectriccooling system 1100C includes cells 1101C, cooling elements 2210C, andorifice plate 1120C having apertures 1122C-1, 1122C-2 and 1122C-3 thatare analogous to cells and their components described herein. Also shownare return path 1140 and entry path 1112 analogous to chimneys1140/return paths 1140/1140A and valve 215/entry path 1112,respectively. However, some of orifices 1122C-1, 1122C-2 and 1122C-3 areat a nonzero acute angle, θ, with respect to normal to the surface ofstructure 1130. Thus, in the embodiment shown, orifices 1122C-1, 1122C-2and 1122C-3 are angled toward the edges of structure 1130. In anotherembodiment, each of the cells 1101C may have orifices analogous toorifices 1122C-2, which are angled away from the center of thecorresponding cell 1101C and toward the return paths 1140.

Piezoelectric cooling system 1100C operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1100C may more efficiently and quietly cool structure1130 at lower power.

FIG. 14D depicts piezoelectric cooling system 1100D. Piezoelectriccooling system 1100D includes cells 1101D, cooling elements 1110D, andorifice plate 1120D having apertures 1122D-1, 1122D-2 and 1122D-3 thatare analogous to cells and their components described herein. Also shownare return path 1140 and entry path 1112 analogous to chimneys240/return paths 1140 and valve 215/entry path 1112, respectively.However, some of orifices 1122D-1, 1122D-2 and 1122D-3 are at a nonzeroacute angle, θ, with respect to normal to the surface of structure 1130.Thus, in the embodiment shown, orifices 1122D-1, 1122D-2 and 1122D-3 areangled toward the center of structure 1130. In another embodiment, eachof the cells 1101D may have orifices analogous to orifices 1122D-2,which are angled toward the center of the corresponding cell 1101D.

Piezoelectric cooling system 1100D operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1100D may more efficiently and quietly cool structure1130 at lower power.

FIGS. 15A-15K are diagrams depicting exemplary embodiments of coolingsystems 1200A, 1200B and 1200C usable with heat-generating structures.For clarity, only certain components are shown and FIGS. 15A-15G are notto scale. Cooling systems 1200A, 1200B, 1200C, 1200D, 122E, 1200F and1200G are used in connection with a structure 1230 analogous tostructure 130 and 230. Structure 1230 generates heat during operationand is desired to be cooled. Cooling systems 1200A, 1200B, 1200C, 1200D,122E, 1200F and 1200G may be MEMS systems having dimensions in theranges described above.

FIG. 15A depicts piezoelectric cooling system 1200A. Piezoelectriccooling system 1200A includes cells 1201, cooling elements 1210, orificeplate 1220 having apertures 422, entry path 1212 and return path 1240that are analogous to cells and their components described herein.Piezoelectric cooling system 1200A operates in an analogous manner topiezoelectric cooling systems described herein.

Structure 1230 includes semiconductor devices 1262, 1264 and 1266.Semiconductor devices 1262, 1264 and 1266 may be integrated circuits1262, 1264 and 1266 residing on substrate 1270. Integrated circuits1262, 1264 and 1266 generate heat during operation and are desired to becooled by piezoelectric cooling system 1200A. Structure 1230 alsoincludes heat spreader 1260, which mitigates the increase in localtemperature near the integrated circuits 1262, 1264 and 1266 by allowingheat to travel across heat spreader 1260. Heat spreader 1260 thus has ahigh thermal conductivity coefficient. Piezoelectric cooling system1200A is used to transfer heat from heat spreader 1260, thereby aidingin cooling integrated circuits 1264, 1264 and 1266. Also shown istemperature sensor 1263 in proximity to integrated circuit 1262. Inother embodiments, other and/or additional integrated circuits 164and/or 1266 might include temperature sensor. Further, a temperaturesensor such as temperature sensor 1265 coupled with orifice plate 1220or analogous structure might be used in addition to or in lieu ofsensors such as sensor 1263. Structure 1230 and piezoelectric coolingsystem 1200A reside within a device having cover 1280. Althoughindicated to be a cover, in other embodiments, structure 1280 may simplybe another portion of the corresponding device in which system 1200A andstructure 1230 reside.

Piezoelectric cooling system 1200A operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1200A may more efficiently and quietly cool heat spreader1260, and thus integrated circuits 1262, 1264 and 1266 of structure 430at lower power. Further, piezoelectric cooling system 1200A may utilizestemperature 1263 sensor 1263 to monitor the temperature of integratedcircuit 1262. Thus, cooling system 1200A may be enabled in response tochanges in temperature detected by temperature sensor 1263 or othertemperature sensor internal to one or more of semiconductor device(s)1262, 1264 and 1266.

FIG. 15B depicts piezoelectric cooling system 1200B. Piezoelectriccooling system 1200B includes cells 1201, cooling elements 1210, orificeplate 1220 having apertures 1222, entry path 1212 and return path 1240that are analogous to cells and their components described herein. Alsoshown is temperature sensor 1263 in proximity to integrated circuit1262. Other and/or additional temperature sensors could be incorporatedfor other heat-generating components. Such sensors may be internaland/or external to the heat-generating components. A temperature sensorsuch as temperature sensor 1265 coupled with orifice plate 1220 oranalogous structure might be used in addition to or in lieu of sensorssuch as sensor 1263.

Structure 1230B is analogous to structure 1230 and thus includesintegrated circuits 1262, 1264 and 1266 residing on substrate 1270.Optional heat spreader 1260 and temperature sensor 1634 are also shown.However, structure 1230B is a packaged structure incorporatingintegrated circuits 1262, 1264 and 1266, which generate heat. Thus,piezoelectric cooling system 400B is mounted on packaged structure 430B.

Piezoelectric cooling system 1200B operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1200B may more efficiently and quietly cool structure1230B, and thus integrated circuits 1262, 1264 and 1266 at lower power.

FIG. 15C depicts piezoelectric cooling system 1200C. Piezoelectriccooling system 1200C includes cells 1201, cooling elements 1210, orificeplate 1220 having apertures 1222, entry path 1212 and return path 1240that are analogous to cells and their components described herein.

Structure 1230C is analogous to structures 1230 and 1230B. Consequently,semiconductor structure 1230C includes integrated circuits 1262, 1264and 1266 residing on substrate 1270 and optional temperature sensor1263. Although only one temperature sensor 1263 is shown, multipletemperature sensors might be employed internal or external to integratedcircuits 1262, 1264 and/or 1266. Further, a temperature sensor such astemperature sensor 1265 coupled with orifice plate 1220 or analogousstructure might be used in addition to or in lieu of sensors such assensor 1263. Optional heat spreader 1260 is also shown. However,structure 1230B is a packaged structure incorporating not onlyintegrated circuits 1262, 1264 and 1266 but also piezoelectric coolingsystem 1200B. Stated differently, piezoelectric cooling system isincorporated into packaged structure 1230C.

Piezoelectric cooling system 1200C operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1200C may more efficiently and quietly cool integratedcircuits 1262, 1264 and 1266 at lower power.

FIGS. 15D and 15E are side and close-up side views of piezoelectriccooling system 1200D used in a device. Piezoelectric cooling system1200D includes cells, cooling element 1210D, orifice plate 1220 havingapertures 1222, entry path 1212, active valve 1280 having apertures 1292and return path (not explicitly shown) that are analogous to cells andtheir components described herein. However, for clarity, such structuresare not shown.

Structure 1230D is analogous to structures 1230, 1230B and 1230C.Consequently, structure 1230D includes integrated circuit 1262 (e.g. achip package) residing on substrate 1270. Substrate 1270 may be aprinted circuit board. Although not shown, internal and/or externaltemperature sensors might be employed. Back cover 1280 is also shown.Cooling system 1200D is attached to a frame in proximity to chip package1262.

Piezoelectric cooling system 1200D operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1200D may more efficiently and quietly cool chip package1262 at lower power. Further, piezoelectric cooling system 1200 mayfunction as an electromagnetic interference (EMI) shield. For example,orifice plate 1220 may function both as a ground and an EMI shield forchip package 1262. Orifices 1222 occupy a small enough fraction of thearea of orifice plate 1220 that orifice plate 1220 can perform shieldingfunctions. Thus, performance of chip package 1262 may be improved.Additional piezoelectric cooling systems 1200D can be employed,piezoelectric cooling system 1200D can be increased in size, for exampleby adding more cells, to cool additional portions of the device.Further, in another embodiment, piezoelectric cooling system 1200Dand/or other analogous piezoelectric cooling systems might be orientedperpendicular to what is shown. Thus fluid is driven across andsubstantially parallel to the top surface of structure 1230D, andsubstantially perpendicular to side surfaces of structure 1230D.

FIG. 15F depicts piezoelectric cooling system 1200F used in a closeddevice. Piezoelectric cooling system 1200F includes cell(s), coolingelement(s), orifice plate(s) having apertures therein, entry path(s),valve(s), return path and other components (not explicitly shown) thatare analogous to cells and their components described herein. However,for clarity, such structures are not shown.

Structure 1230F is analogous to structures 1230, 1230B, 1230C and 1230D.Consequently, structure 1230F includes component 1262 (e.g. a chippackage) residing on substrate 1270. Substrate 1270 may be a printedcircuit board. Also shown are components 1264, 1266 and 1267 which maybe integrated circuits or other components. Although not shown, internaland/or external temperature sensors as well as other componentsincluding but not limited to a heat spreader might be employed. Cover1280 is also shown. Cooling system 1200F is attached to a frame inproximity to component 1262.

Piezoelectric cooling system 1200F operates in a manner analogous topiezoelectric cooling systems described herein. As can be seen by arrowsin FIG. 15F, cool fluid (e.g. air) near component 1267 is drawn towardpiezoelectric cooling device 1200F. Piezoelectric cooling system 1200Fdrives fluid from its distal to the proximal side. Thus, fluid is driventoward component 1262 as described herein. The fluid exits the regionfrom near the sides of component 1262 carrying heat from component 1262away. Thus, piezoelectric cooling system 1200F may more efficiently andquietly cool component 1262 at lower power. Thus, performance ofcomponent 1262 may be improved. Additional piezoelectric cooling systemscan be employed, piezoelectric cooling system 1200F can be increased insize, for example by adding more cells, to cool additional portions ofthe device, such as components 1264 and 1266. Further, in anotherembodiment, piezoelectric cooling system 1200F might be orientedperpendicular to what is shown. In such an embodiment, piezoelectriccooling system 1200F may be used to drive fluid flow across components1262, 1264, 1266 and 1267.

FIG. 15G depict piezoelectric cooling systems 1200G-1, 1200G-2 and1200G-3 used in a device with vents. Each piezoelectric cooling system1200G-1, 1200G-2 and 1200G-3 includes cell(s), cooling element(s),orifice plate(s) having apertures therein, entry path(s), valve(s),return path(s) and other components (not explicitly shown) that areanalogous to cells and their components described herein. For clarity,such structures are not shown.

Structure 1230G is analogous to structures 1230, 120B, 1230C, 120D and1230F. Consequently, structure 1230G includes component 1262 (e.g. achip package) residing on substrate 1270. Substrate 1270 may be aprinted circuit board. Also shown are vents 1294. Although not shown,internal and/or external temperature sensors as well as other componentsincluding but not limited to a head spreader may be used.

Piezoelectric cooling systems 1200G-1, 1200G-2 and 1200G-3 operate in amanner analogous to piezoelectric cooling systems described herein. Ascan be seen by arrows in FIG. 15G, cool fluid (e.g. air) outside of thesystem is drawn in through vent 1294. This occurs because of thepiezoelectric cooling system 1200G-1, which operates in a manneranalogous to a fan. Fluid travels to the distal side of piezoelectriccooling system 1200G-2, which drives fluid from its distal to theproximal side. Thus, fluid is driven toward component 1262 as describedherein. The fluid exits the region from near the sides of component 1262carrying heat from component 1262 away. Piezoelectric cooling system1200G-3 drives fluid out of the system through vent 1294. Piezoelectriccooling system, therefore, generates fluid flow throughout the system tobetter dissipate heat generated by component 1262. Thus, piezoelectriccooling system 1200G may more efficiently and quietly cool component1262 at lower power. Thus, performance of component 1262 may beimproved. Additional piezoelectric cooling systems 1200G can beemployed, piezoelectric cooling system 1200G can be increased in size,for example by adding more cells, to cool additional portions of thedevice. Further, piezoelectric cooling system 1200G-2 may be omitted insome embodiments. In such embodiments, piezoelectric cooling systems,such as systems 1200G-1 and 1200G-3, may generate fluid flow through thesystem. In some such embodiments, additional piezoelectric coolingsystems could be oriented as indicated in FIG. 11 (perpendicular to theorientation of piezoelectric cooling system 1200G-2), to drive fluidflow along the surfaces between piezoelectric cooling systems 1200G-1and 1200G-3.

FIG. 15H depicts piezoelectric cooling system 1200H used in cooling astructure. Piezoelectric cooling system 1200H includes cell(s), coolingelement(s), orifice plate(s) having apertures therein, entry path(s),valve(s), return path and other components (not explicitly shown) thatare analogous to cells and their components described herein. However,for clarity, such structures are not shown.

Structure 1230H is analogous to structures 1230, 1230B, 1230C, 1230D,1230F and 1230G-1 through 1230G-3. Consequently, structure 1230Hincludes component 1262 (e.g. a chip package) residing on substrate1270. Substrate 1270 may be a printed circuit board. Also shown is heatspreader 1260H. Although not shown, internal and/or external temperaturesensors as well as other components. Cover 1280 is also shown. Coolingsystem 1200H is attached to a frame in proximity to heat spreader 1230H.Thus, heat spreader 1260H spreads heat from component 1262 over a largerarea and piezoelectric cooling system 1200H cools this larger area ofhead spreader 1260H.

Piezoelectric cooling system 1200H operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1200H may more efficiently and quietly cool component1262 at lower power.

FIG. 15I depicts piezoelectric cooling system 1200I used in cooling astructure. Piezoelectric cooling system 1200I includes cell(s), coolingelement(s), orifice plate(s) having apertures therein, entry path(s),valve(s), return path and other components (not explicitly shown) thatare analogous to cells and their components described herein. However,for clarity, such structures are not shown.

Structure 1230I is analogous to structures 1230, 1230B, 1230C, 1230D,1230F, 1230G-1 through 1230G-3 and 1230H. Consequently, structure 1230Iincludes component 1262 (e.g. a chip package) residing on substrate1270. Substrate 1270 may be a printed circuit board. Also shown is heatpipe 12601. Although not shown, internal and/or external temperaturesensors as well as other components. Cover 1280 is also shown. Coolingsystem 1200I is attached to a frame in proximity to heat pipe 12601.Heat pipe 12601 transfers heat from component 1262. Heat pipe 1260 maycarry a liquid that transitions to a vapor phase in order to coolcomponent 1262. The vapor is carried away from component 1262 by heatpipe 12601. Piezoelectric cooling system 1200I then cools heat pipe12601. In some embodiments, this cooling may be sufficient that thevapor transitions back to a liquid phase. Thus, piezoelectric coolingsystem 1200I may act as part of a heat exchanger.

Piezoelectric cooling system 1200I operates in a manner analogous topiezoelectric cooling systems described herein. Piezoelectric coolingsystem 1200I cools heat pipe 12601 and, therefore, component 1262. Thus,piezoelectric cooling system 1200I may more efficiently and quietly coolcomponent 1262 at lower power.

FIG. 15J depicts piezoelectric cooling system 1200J used in cooling astructure. Piezoelectric cooling system 1200J includes cell(s), coolingelement(s), orifice plate(s) having apertures therein, entry path(s),valve(s), return path and other components (not explicitly shown) thatare analogous to cells and their components described herein. However,for clarity, such structures are not shown.

Structure 1230J is analogous to structures 1230, 1230B, 1230C, 1230D,1230F, 1230G-1 through 1230G-3, 1230H and 1230I. Consequently, structure1230J includes component 1262 (e.g. a chip package) residing onsubstrate 1270. Substrate 1270 may be a printed circuit board. Alsoshown is vapor chamber 1260J that is analogous to heat pipe 12601.Although not shown, internal and/or external temperature sensors as wellas other components. Cover 1280 is also shown. Cooling system 1200J isattached to a frame in proximity to vapor chamber 1260J. Piezoelectriccooling system 1200J cools vapor chamber 1260J. In some embodiments,this cooling may be sufficient that the vapor transitions back to aliquid phase. Thus, piezoelectric cooling system 1200I may act as partof a heat exchanger.

Piezoelectric cooling system 1200J operates in a manner analogous topiezoelectric cooling systems described herein. Piezoelectric coolingsystem 1200J cools vapor chamber 1260J and, therefore, component 1262.Thus, piezoelectric cooling system 1200J may more efficiently andquietly cool component 1262 at lower power.

FIG. 15K depicts piezoelectric cooling system 1200K used in cooling astructure. Piezoelectric cooling system 1200K includes cell(s), coolingelement(s), orifice plate(s) having apertures therein, entry path(s),valve(s), return path and other components (not explicitly shown) thatare analogous to cells and their components described herein. However,for clarity, such structures are not shown.

Structure 1230K is analogous to structures 1230, 1230B, 1230C, 1230D,1230F, 1230G-1 through 1230G-3, 1230H, 1230I and 1230J. Consequently,structure 1230K includes component 1262 (e.g. a chip package) residingon substrate 1270. Also shown is an additional component 1264 (e.g. anadditional chip package) residing on substrate 1270. Although not shown,internal and/or external temperature sensors as well as othercomponents. Substrate 1270 may be a printed circuit board. Cover 1280 isalso shown. Cooling system 1200K is attached to a frame in proximity toboth components 1262 and 1264. Thus, piezoelectric cooling system 1200Kmay extend over a large area.

Piezoelectric cooling system 1200K operates in a manner analogous topiezoelectric cooling systems described herein. Thus, piezoelectriccooling system 1200K may more efficiently and quietly cool components1262 and 1264 at lower power.

FIG. 16 is a diagram depicting an exemplary embodiment of apiezoelectric cooling system 1300 usable with a heat generatingstructure. For clarity, only certain components are shown and FIG. 16 isnot to scale. Piezoelectric cooling system 1300 is used in connectionwith a structure 1320. Structure 1320 generates heat during operationand is desired to be cooled.

Piezoelectric cooling system 1300 includes multiple cells 1301 each ofwhich includes a piezoelectric blade element 1310. Cells 1301 may havethe same size range as described above such that S is at least threemillimeters and not more than five millimeters. Piezoelectric bladeelements 1310 are oriented at angle ϕ when quiescent. When actuated,piezoelectric blade elements 510 vibrate between angles ϕ1 and ϕ2. Insome embodiments, the angle of vibration (ϕ2−ϕ1) is at least fivedegrees and not more than twenty degrees. The lengths of thepiezoelectric blade elements 510 may vary depending upon the distance tostructure 1330 and the angle of operation. For example, the vibratingportion of blade elements 1310 may be at least one millimeter and notmore than five millimeters in length. In some embodiments, the frequencyof vibration is nominally 300 Hz. In some embodiments, ϕ is nominallythirty degrees and h is nominally two hundred fifty microns. The top ofeach piezoelectric blade element 1310 is a distance, d, above thesurface of structure 1320. In some embodiments, d is at least threehundred microns and not more than five hundred microns.

In operation, piezoelectric blade elements 1310 vibrate, drawing fluidfrom the distal side of one piezoelectric element to the proximal sideof another piezoelectric element. This motion of the fluid can be seenby the curved arrows in FIG. 16. Because the fluid is driven along thesurface of structure 1330, the fluid can carry heat away from structure1330. Thus, piezoelectric cooling system 1300 can cool structure 1330more efficiently than, for example, an electric fan. In someembodiments, cooling cells such as cells 701 (rotated ninety degrees) or801 might be used. In addition, piezoelectric cooling structure 1300 canbe combined with one or more of piezoelectric cooling structures 100,100A, 200, 1100A, 1100B, 1100C, 1100D, 1200A, 1200B and/or 1200C. Insuch an embodiment, piezoelectric blade elements 1310 can aid in drawingair along the corresponding heat generating structure. For example, FIG.1D indicates that fluid is driven not only through orifices 122, butalso along the surface of structure 130. This might be accomplishedusing sets of piezoelectric blade elements 1310. Thus, piezoelectriccooling system 1300 might further improve cooling of piezoelectriccooling structures described herein.

FIGS. 17A-17B are diagrams depicting exemplary embodiments of coolingsystems 1400A and 1400B usable with a structure. For clarity, onlycertain components are shown and FIGS. 17A-17B are not to scale. Coolingsystems 1400A and 1400B are used in connection with structure 1430analogous to structures described above. Cooling systems 1400A and 1400Bmay be MEMS systems having dimensions in the ranges described above andin proximity to the structures 1430 desired to be cooled as describedabove.

FIG. 17A depicts piezoelectric cooling system 1400A including cells1401A and 1451A. Each cell 1401A includes cooling element 1410 andorifice plate 1420 having apertures 1422 that are analogous to cells,piezoelectric cooling elements, and orifice plates having aperturesdescribed herein. For simplicity, valve and apertures in cooling element1410 are represented by entry path 1412. Return path, or chimney 1440,between cells 1401A are also shown. Cells 1451A are analogous to cells1301 and thus include blades 1460A. Blades 1460A together can move fluidfrom the distal side to the proximal side of the collection of cells1451A. Stated differently, blades 1460A may move fluid that has returnedfrom near structure 1430 through chimneys/return paths 1440. Inaddition, blades 1460A move fluid from the distal side of blades 1460Ato the proximal side of blades 1460A.

Cells 1401A operate in an analogous manner to piezoelectric coolingsystems described herein. Thus, cooling elements 1410 generate jets ofair generally directed toward structure 1430. Cells 1451A move fluidalong the surface of structure 1430 in the direction shown by arrows inFIG. 17A. Thus, in addition to cells 1401A cooling structure 1430, cells1451A may move the fluid to which heat from structure 1430 has beentransferred along the surface of structure 1430. Thus, in addition tothe benefits of piezoelectric cooling systems described herein, the heatmay be more effectively carried away.

FIG. 17B depicts piezoelectric cooling system 1400B including cells1401B and 1451B. Each cell 1401B includes cooling element 1410 andorifice plate 1420 having apertures 1422 that are analogous to cells,piezoelectric cooling elements, and orifice plates having aperturesdescribed herein. For simplicity, valve and apertures in cooling element1410 are represented by entry path 1412. Return path, or chimney 1440,between cells 1401B are also shown. Cells 1451B are analogous to cells701 and thus include cooling elements 1460B and orifice plates 1461having apertures therein.

Cells 1401B operate in an analogous manner to piezoelectric coolingsystems described herein. Thus, cooling elements 1410 generate jets ofair generally directed toward structure 1430. Cells 1451B move fluidalong the surface of structure 1430 in the direction shown by arrows inFIG. 17B. Thus, in addition to cells 1401B cooling structure 1430, cells1451B may move the fluid to which heat from structure 1430 has beentransferred along the surface of structure 1430. Thus, in addition tothe benefits of piezoelectric cooling systems described herein, the heatmay be more effectively carried away.

FIG. 18 is a plan view of an exemplary embodiment of cooling cells 1501usable with a heat-generating structure. For clarity, only certaincomponents are shown and FIG. 18 is not to scale. Piezoelectric coolingcell 1501 is used in connection with a semiconductor structure orelectronic device 1502. Piezoelectric cooling cells 1501 are analogousto one or more of cooling cells described herein having cooling elementsthat move fluid from a distal to a proximal side of the cooling element.In an alternate embodiment, one or more of cooling cells 1400 may beanalogous to cells 1301. Although as including the same cells, one ormore of the arrays may include different cells. For example, cellshaving active valves, cells having passive valves and/or cells not usingvalves may be mixed within a single array and/or between multiplearrays.

Multiple piezoelectric cooling cells 1501 are distributed acrosselectronic device 1502. In the embodiment shown, three groups ofpiezoelectric cooling cells 1501 are shown. In particular, a 1×1rectangular array (shown as having a larger cooling cell 1501), a 3×2rectangular array and a 3×1 rectangular array of piezoelectric coolingcells 1501 are shown. In some embodiments, each of the arrays is inproximity to a different structure, such as an integrated circuit, thatgenerates heat and is desired to be cooled. Some or all of the arraysare within a semiconductor package in a manner analogous to coolingsystem 1200C in some embodiments. In other embodiments, some or all ofthe arrays are outside of a semiconductor package in a manner analogousto cooling system 1200B. Other shapes and sizes of arrays are possible.In some embodiments, the 1×1 array, 3×2 array and 3×1 array may beindividually driven. In some embodiments, each individual cell 1501 inone or more of the arrays may be individually driven. Further, in someembodiments, one or more of cells 1501 may be activated to varyingamplitudes of deflection of the corresponding cooling elements. Thus,varying sizes, numbers, configurations and activation of piezoelectriccooling cells 1501 can be utilized to cool hot spots of an electronicsdevice.

FIG. 19 is a diagram depicting an exemplary embodiment of a mobiledevice 1600 incorporating a piezoelectric cooling system. For clarity,only certain components are shown and FIG. 19 is not to scale. Mobiledevice 1600 may be a smartphone or other analogous device. Mobile device1600 includes display stack 1610, midframe 1620, heat generatingstructure 1650, heat spreader 1660, piezoelectric cooling systems 1670and 1672 and back cover 1680. For example, heat generating structure1650 may include one or more chipsets and printed circuit board(s)(PCB). Also shown are airgaps 1690, 1692, 1694 and 1696, which may beone hundred microns or more thick. Components 1610, 1620, 1650, and 1680already in mobile device 1600 generally range in thickness from 0.5millimeter through two millimeters. As described above, piezoelectriccooling systems 1670 and 1672 may each be five hundred microns (0.5millimeter) thick or less. In other embodiments, more or fewerpiezoelectric cooling systems may be employed. Thus, piezoelectriccooling systems 1670 and/or 1672 may be incorporated into mobile device1600 without significantly altering its thickness. Piezoelectric coolingsystems 1670 and/or 1672 may have one or more arrays of cooling cells.The arrays and/or cooling cells within the arrays may be selectivelydriven, as described herein. Piezoelectric cooling system 1670 may andmay be used to cool multiple components, such as multiple integratedcircuits in chipset(s) 1650, sensors, one or more batteries (notexplicitly depicted but which may be coupled to PCB 1640) and/or othercomponents. Further, although two piezoelectric cooling systems 1670 and1672 are shown as incorporated into mobile device 1600 at a particularlocation, in other embodiments, one or more piezoelectric coolingsystems might be incorporated at other and/or additional locations. Inthe embodiment shown, chipset 1650 is cooled by correspondingpiezoelectric cooling system 1670 and 1672. In other embodiments, moreor fewer piezoelectric cooling systems may be used. For example, aparticular chipset 1650 may be cooled from both sides. Otherconfigurations are possible. Thus, the benefits of significant coolingthat may be quiet and at relatively low power due to resonance may beachieved without substantially increasing the thickness of mobile device1600.

FIG. 20A is a diagram depicting an exemplary embodiment of coolingsystem 1700 and associated electronics. For clarity, only certaincomponents are shown and FIG. 20A is not to scale. Cooling system 1700is a piezoelectric cooling system analogous to those described herein.In the embodiment shown, piezoelectric cooling system 1700 includescells 1701 having chimneys (unlabeled circles) between the cells. Cells1701 are analogous to cells described herein that include a coolingelement that moves fluid from the distal to the proximal side of thecooling element and may include an orifice plate having orificestherein. Also included in piezoelectric cooling system are cells 1710that are analogous to cells 1301, 1451A or 1451B. Thus, piezoelectriccooling system 1700 is analogous to piezoelectric cooling system 1400Aor 1400B. In other embodiments, other configurations may be used.Further additional and/or other arrays of cooling cells may be used.

Also shown are processor 1740 and power source 1750 that may be a powermanagement integrated circuit (PMIC) that may be part of the componentsalready present in the mobile or other device in which cooling system1700 is used. Although shown as distal from cooling system 1700, in someembodiments processor and/or power source 1750 may be cooled usingcooling system 1700. Also shown are electronics 1720, interface 1730 andcontroller 1760. Interface 1730 communicates with processor 1740 andpower source 1750, as well as any desired remaining components of thedevice. For example, interface 1730 may receive signals from temperaturesensors located on portions of the device which are desired to becooled. Power to piezoelectric cooling system 1700 is also provided frompower source 1750 via interface 1730. Electronics 1720 includes acommunications interface for receiving control signals and addressingcircuitry for selectively activating individual cells 1701 or groups ofcells 1701. For example, addressing circuitry might include row andcolumn selectors managed by controller 1760. Controller 1760 thusselectively drives cells 1701 via electronics 1720. In some embodiments,software used to control piezoelectric cooling system 1700 isimplemented by processor 1740. For example, processor 1740 may implementsoftware used to tune piezoelectric cooling elements to resonance. Thus,individual cells 1701 or groups of cells 1701 can be selectively driven.Further, although a single array 1700 is shown, multiple arrays may bedriven using the same electronics 1720, 1730, 1740, 1750 and 1760. Sucha system is shown in FIG. 20B, in which array 1700B including cells1701B is also driven.

FIG. 21 is a flow chart depicting an exemplary embodiment of method 1800for operating a cooling system. Method 1800 may include steps that arenot depicted for simplicity. Method 1800 is described in the context ofpiezoelectric cooling system 100. However, method 1800 may be used withother cooling systems including but not limited to systems and cellsdescribed herein. Method 1800 may be performed using controller 1760and/or processor 1740.

The cells 101 to be driven are selected for driving at 1802. Thus, somecells in an array may be left dormant or driven at another time. Theselection of cells 101 to be driven at 1802 may be based upon heat in agiven region, for example as measured by a temperature sensor such assensor 1263. In some embodiments, an increase in clock speed of aprocessor is expected to generate heat and thus may be used toproactively select cells 101 in the vicinity of the processor foractivation. Thus, the selection of cells 101 to be driven may be basedon a clock measurement or a measurement of junction temperature (e.g. ahigher junction temperature) that indicates that clock speed is high.Cells 101 selected to be driven may be based upon predicted heatgeneration for a particular region because of use of certainfunction(s). For example, in response to a pattern of usage such asvideo streaming for longer times, daily usage patterns or otheractivities, processor 1740 may be predicted to generate heat. Based uponthis prediction, cells 101 in proximity to the processor may beactivated. Accessing certain function(s) which may consume power, use ofparticular interfaces such as communications interfaces for a mobile ornon-mobile device or other activities which have or are expected togenerate heat may result in one or more nearby cells 101 being selectedfor activation at 1802.

If piezoelectric cooling element 110 is to be driven at or nearresonance, then the system is optionally tuned for the resonance ofcooling element 110, at 1804. In some embodiments, this includesconfiguring cooling elements 110 to have the appropriate size, materialproperties, stiffness and robustness to be operated at resonance. Inaddition, cooling elements 110 are also designed to have a resonance ator around the desired range for driving. For example, if thepiezoelectric cooling element is desired to be driven at ultrasonicfrequencies (at or above 15 kHz), then piezoelectric cooling element 110is designed to have a resonance frequency in this range. However,individual piezoelectric cooling elements 110 may have variations intheir resonant frequency. As such, 1804 also includes calibrating andadjusting the driving frequency to match a resonant frequency of thepiezoelectric cooling elements 110.

One or more of the piezoelectric cooling elements 110 are then driven atthe desired frequency, at 1806. At 1806, the amplitude of deflection forcooling elements 110 may be controlled. Thus, a cooling element may butneed not be driven at the maximum possible amplitude. Further, ifmultiple cells 101 are driven, this may be carried out such that certaincells 101 are driven at different phases. For example, adjacent cellsmay be driven with a particular phase difference including but notlimited to being one hundred and eighty degrees out of phase. As part of1804, power used to drive piezoelectric cooling elements 110 may bereduced once resonance is achieved. The mechanical resonance andunder-damping of cooling system 100 may be utilized to reduce, orminimize, power expended in cooling. Thus, sufficient power to maintainvibration of cooling elements 110 at or near the resonance frequency maybe maintained. Consequently, piezoelectric cooling elements 110 operateas described above. Method 1800 thus provides for use of piezoelectriccooling systems described herein. Thus, piezoelectric cooling systemsmay more efficiently and quietly cool semiconductor devices at lowerpower.

FIG. 22 is a flow chart depicting an exemplary embodiment of method 1900for operating a cooling system. Method 1900 may include steps that arenot depicted for simplicity. Method 1900 is described in the context ofpiezoelectric cooling system 100. However, method 1900 may be used withother cooling systems including but not limited to systems and cellsdescribed herein. Method 1900 may also be considered part of method1800. Method 1900 may be performed using controller 1760 and/orprocessor 1740.

The local temperatures of portions of the structure/device to be cooledare measured at 1902. For example, the processor subsystems zonetemperatures, battery temperature, sensor temperature, active antennaarray temperature or other temperature of interest may be measured at1902.

Based on this temperature, one or more of piezoelectric cooling element110 in the region is driven at or near resonance, at 1904. At 1904, theamplitude, phase, and other aspects of driving cooling elements 110 maybe selected and updated. Further, as piezoelectric cooling system 100cools the desired structure 130, the voltage, phase, frequency and/orother parameters used in driving cooling elements 110 may be adjusted.Thus, piezoelectric cooling systems may more efficiently and quietlycool semiconductor devices at lower power.

FIG. 23 is a flow chart depicting an exemplary embodiment of method 2000for operating a cooling system. Method 2000 may include steps that arenot depicted for simplicity. Method 2000 is described in the context ofpiezoelectric cooling system 100. However, method 2000 may be used withother cooling systems including but not limited to systems and cellsdescribed herein. Method 2000 may be performed using controller 1760and/or processor 1740.

The cells 101 to be driven are selected for driving based upon heatgenerated or a prediction of heat generated, at 2002. 2002 may includemeasuring temperature in the vicinity of the desired components,monitoring processor clock speed, monitoring battery use, monitoring thefunctions selected for use or other aspects of the device. Based on thisinformation, whether and how to drive cell(s) is determined at 2002. Forexample, in response to a pattern of video streaming or otheractivities, heat may be predicted to be generated. Based upon thisprediction, cells 101 in proximity to the processor subsystem zones maybe activated. Accessing certain function which may consume power, use ofparticular interfaces such as communications interfaces for a mobile orother device or other activities which have or are expected to generateheat may result in one or more nearby cells 101 being selected foractivation at 1802.

The selected piezoelectric cooling element(s) 110 are driven at thedesired frequency, at 2004. At 2004, the amplitude of deflection forcooling element(s) 110, driving frequency, phase, and other aspects ofoperation of piezoelectric cooling system 100 may be controlled. Method2000 thus provides for use of piezoelectric cooling systems describedherein. Thus, piezoelectric cooling systems may more efficiently andquietly cool electronic devices at lower power.

Thus, various embodiments of cooling structures, their components, andmethod of operations have been disclosed. Various features may beomitted and/or combined in ways not explicitly disclosed herein. As aresult, cooling of heat-generating structures may be improved.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. A cooling system comprising: a plurality ofindividual piezoelectric cooling elements spatially arranged in an arrayextending in at least two dimensions; a communications interfaceassociated with the individual piezoelectric cooling elements such thatselected individual piezoelectric cooling elements within the array canbe activated based at least in part on heat energy generated in thevicinity of the selected individual piezoelectric cooling elements; anddriving circuitry associated with the individual piezoelectric coolingelements configured to drive the selected individual piezoelectriccooling elements; wherein the driving circuitry is configured to drive afirst portion of the plurality of individual piezoelectric coolingelements at a first frequency and a second portion of the plurality ofindividual piezoelectric cooling elements at a second frequencydifferent from the first frequency.
 2. The cooling system of claim 1,wherein the driving circuitry drives the selected individualpiezoelectric cooling elements to be partially activated such that anamplitude of deflection of the selected piezoelectric cooling elementsis variable.
 3. The cooling system of claim 1, wherein the drivingcircuitry drives the selected individual piezoelectric cooling elementsto be on or off such that amplitudes of deflection of the selectedindividual piezoelectric elements are substantially equal.
 4. Thecooling system of claim 1, further comprising: an interface coupled withthe driving circuitry and for receiving at least one temperature readingfrom at least one temperature sensor of at least one heat generatingstructure in the vicinity of the selected individual piezoelectriccooling elements.
 5. The cooling system of claim 4, wherein the at leastone heat generating structure includes a first heat generating structureand a second heat generating structure, a first portion of the pluralityof individual piezoelectric cooling elements is in the vicinity of thefirst heat generating structure having a first temperature, a secondportion of the plurality of individual piezoelectric cooling elements isin the vicinity of the second heat generating structure having a secondtemperature, the first portion of the plurality of individualpiezoelectric cooling elements being separately addressable from thesecond portion of the plurality of individual piezoelectric coolingelements.
 6. The cooling system of claim 1, wherein the communicationsinterface receives at least one temperature reading from at least onetemperature sensor in the vicinity of the selected individualpiezoelectric cooling elements.
 7. The cooling system of claim 1,wherein the cooling system is coupled with a semiconductor package, afirst portion of the plurality of individual piezoelectric coolingelements being in the vicinity of a first portion of the semiconductorpackage, a second portion of the plurality of individual piezoelectriccooling elements being in the vicinity of a second portion of thesemiconductor package, the first portion of the plurality of individualpiezoelectric cooling elements being separately addressable from thesecond portion of the plurality of individual piezoelectric coolingelements.
 8. The cooling system of claim 7, wherein the array includes aplurality of rows and a plurality of columns, the address circuitryfurther comprising: row and column address circuitry.
 9. The coolingsystem of claim 1, further comprising: address circuitry coupled withthe plurality of individual piezoelectric cooling elements and thecommunications interface such that each of the plurality of individualpiezoelectric cooling elements is separately addressable.
 10. Thecooling system of claim 1, wherein the communication interface includesfurther includes a bus.
 11. The cooling system of claim 1, wherein thedriving circuitry is further configured to separately drive portions ofthe plurality of individual piezoelectric cooling elements in acoordinated pattern.
 12. The cooling system of claim 1, wherein thedriving circuitry is configured to drive the plurality of individualpiezoelectric cooling elements at an ultrasonic frequency.
 13. Thecooling system of claim 12, wherein the ultrasonic frequency is aresonance frequency for the individual piezoelectric cooling element.14. The piezoelectric cooling system of claim 1, further comprising: anadditional plurality of piezoelectric cooling elements spatiallyarranged in an additional array, the additional plurality of coolingelements being coupled with the communications interface and driven bythe driving circuitry.
 15. A cooling system, comprising: a plurality ofindividual piezoelectric cooling elements spatially arranged in an arrayextending in at least two dimensions; a communications interfaceassociated with the individual piezoelectric cooling elements such thatselected individual piezoelectric cooling elements within the array canbe activated based at least in part on heat energy generated in thevicinity of the selected individual piezoelectric cooling elements;driving circuitry associated with the individual piezoelectric coolingelements configured to drive the selected individual piezoelectriccooling elements; and a plurality of exhaust chimneys interspersedbetween the plurality of individual piezoelectric cooling elements inthe array.
 16. A cooling system, comprising: a plurality of individualpiezoelectric cooling elements spatially arranged in an array extendingin at least two dimensions; a communications interface associated withthe individual piezoelectric cooling elements such that selectedindividual piezoelectric cooling elements within the array can beactivated based at least in part on heat energy generated in thevicinity of the selected individual piezoelectric cooling elements;driving circuitry associated with the individual piezoelectric coolingelements configured to drive the selected individual piezoelectriccooling elements; and a plurality of valves corresponding to at least aportion of the plurality of piezoelectric cooling elements.
 17. Apiezoelectric cooling system, comprising: a plurality of arrays, each ofthe plurality of arrays extending in at least two dimensions andincluding a plurality of individual piezoelectric cooling elements, eachof the plurality of arrays having a thickness not exceeding five hundredmicrons; a communications interface coupled with the plurality ofarrays, associated with the individual piezoelectric cooling elementssuch that selected individual piezoelectric cooling elements within eachof the plurality of arrays can be activated; and driving circuitryassociated with the individual piezoelectric cooling elements configuredto drive the selected individual piezoelectric cooling elements in eachof the plurality of arrays; wherein the driving circuitry is configuredto drive a first portion of the plurality of individual piezoelectriccooling elements at a first frequency and a second portion of theplurality of individual piezoelectric cooling elements at a secondfrequency different from the first frequency.
 18. The piezoelectriccooling system of claim 17, wherein the plurality of arrays isconfigured to cool a plurality of heat-generating structures, each ofthe plurality of arrays being configured to address a different one ofthe plurality of heat-generating structures.
 19. The piezoelectriccooling system of claim 17, wherein the driving circuitry selectively isdrives each of the plurality of arrays.
 20. The piezoelectric coolingsystem of claim 17, wherein the driving circuitry selectively driveseach of the plurality of individual cooling elements in each of theplurality of arrays.
 21. A method of cooling a device comprising:selectively driving at least a portion of a plurality of individualpiezoelectric cooling elements, the plurality of individualpiezoelectric cooling elements spatially arranged in an array extendingin at least two dimensions, the plurality of individual piezoelectriccooling elements being activated based at least in part on heat energygenerated in a vicinity of the plurality of individual piezoelectriccooling elements, the driving being configured to drive a first portionof the plurality of individual piezoelectric cooling elements at a firstfrequency and a second portion of the plurality of individualpiezoelectric cooling elements at a second frequency different from thefirst frequency.
 22. The method of claim 21 wherein the driving furtherincludes: driving the portion of the plurality of individualpiezoelectric cooling elements such that each of the portion of theplurality of individual piezoelectric cooling elements vibrates at afrequency of at least 15 kHz.
 23. The method of claim 22, wherein thefrequency is substantially at a resonance frequency of each of theportion of the plurality of individual piezoelectric cooling elements.24. The method of claim 23, further comprising: tuning the plurality ofindividual piezoelectric cooling elements to the at least one resonancefrequency.